157 results on '"Cockell, Charles S."'
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2. The Concept of Life on Venus Informs the Concept of Habitability.
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Cockell, Charles S., Hallsworth, John E., McMahon, Sean, Kane, Stephen R., and Higgins, Peter M.
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An enduring question in astrobiology is how we assess extraterrestrial environments as being suitable for life. We suggest that the most reliable assessments of the habitability of extraterrestrial environments are made with respect to the empirically determined limits to known life. We discuss qualitatively distinct categories of habitability: empirical habitability that is constrained by the observed limits to biological activity; habitability sensu stricto, which is defined with reference to the known or unknown limits to the activity of all known organisms; and habitability sensu lato (habitability in the broadest sense), which is circumscribed by the limit of all possible life in the universe, which is the most difficult (and perhaps impossible) to determine. We use the cloud deck of Venus, which is temperate but incompatible with known life, as an example to elaborate and hypothesize on these limits. [ABSTRACT FROM AUTHOR]
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- 2024
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3. Planning Implications Related to Sterilization-Sensitive Science Investigations Associated with Mars Sample Return (MSR).
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Velbel, Michael A., Cockell, Charles S., Glavin, Daniel P., Marty, Bernard, Regberg, Aaron B., Smith, Alvin L., Tosca, Nicholas J., Wadhwa, Meenakshi, Kminek, Gerhard, Meyer, Michael A., Beaty, David W., Carrier, Brandi Lee, Haltigin, Timothy, Hays, Lindsay E., Agee, Carl B., Busemann, Henner, Cavalazzi, Barbara, Debaille, Vinciane, Grady, Monica M., and Hauber, Ernst
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VAN der Waals forces , *LIFE sciences , *SCIENCE journalism , *MATERIALS at low temperatures , *BIOMOLECULES , *LIE detectors & detection - Abstract
The NASA/ESA Mars Sample Return (MSR) Campaign seeks to establish whether life on Mars existed where and when environmental conditions allowed. Laboratory measurements on the returned samples are useful if what is measured is evidence of phenomena on Mars rather than of the effects of sterilization conditions. This report establishes that there are categories of measurements that can be fruitful despite sample sterilization and other categories that cannot. Sterilization kills living microorganisms and inactivates complex biological structures by breaking chemical bonds. Sterilization has similar effects on chemical bonds in non-biological compounds, including abiotic or pre-biotic reduced carbon compounds, hydrous minerals, and hydrous amorphous solids. We considered the sterilization effects of applying dry heat under two specific temperature-time regimes and the effects of γ-irradiation. Many measurements of volatile-rich materials are sterilization sensitive—they will be compromised by either dehydration or radiolysis upon sterilization. Dry-heat sterilization and γ-irradiation differ somewhat in their effects but affect the same chemical elements. Sterilization-sensitive measurements include the abundances and oxidation-reduction (redox) states of redox-sensitive elements, and isotope abundances and ratios of most of them. All organic molecules, and most minerals and naturally occurring amorphous materials that formed under habitable conditions, contain at least one redox-sensitive element. Thus, sterilization-sensitive evidence about ancient life on Mars and its relationship to its ancient environment will be severely compromised if the samples collected by Mars 2020 rover Perseverance cannot be analyzed in an unsterilized condition. To ensure that sterilization-sensitive measurements can be made even on samples deemed unsafe for unsterilized release from containment, contingency instruments in addition to those required for curation, time-sensitive science, and the Sample Safety Assessment Protocol would need to be added to the Sample Receiving Facility (SRF). Targeted investigations using analogs of MSR Campaign-relevant returned-sample types should be undertaken to fill knowledge gaps about sterilization effects on important scientific measurements, especially if the sterilization regimens eventually chosen are different from those considered in this report. Executive Summary: A high priority of the planned NASA/ESA Mars Sample Return Campaign is to establish whether life on Mars exists or existed where and when allowed by paleoenvironmental conditions. To answer these questions from analyses of the returned samples would require measurement of many different properties and characteristics by multiple and diverse instruments. Planetary Protection requirements may determine that unsterilized subsamples cannot be safely released to non-Biosafety Level-4 (BSL-4) terrestrial laboratories. Consequently, it is necessary to determine what, if any, are the negative effects that sterilization might have on sample integrity, specifically the fidelity of the subsample properties that are to be measured. Sample properties that do not survive sterilization intact should be measured on unsterilized subsamples, and the Sample Receiving Facility (SRF) should support such measurements. This report considers the effects that sterilization of subsamples might have on the science goals of the MSR Campaign. It assesses how the consequences of sterilization affect the scientific usefulness of the subsamples and hence our ability to conduct high-quality science investigations. We consider the sterilization effects of (a) the application of dry heat under two temperature-time regimes (180°C for 3 hours; 250°C for 30 min) and (b) γ-irradiation (1 MGy), as provided to us by the NASA and ESA Planetary Protection Officers (PPOs). Measurements of many properties of volatile-rich materials are sterilization sensitive—they would be compromised by application of either sterilization mode to the subsample. Such materials include organic molecules, hydrous minerals (crystalline solids), and hydrous amorphous (non-crystalline) solids. Either proposed sterilization method would modify the abundances, isotopes, or oxidation-reduction (redox) states of the six most abundant chemical elements in biological molecules (i.e., carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulphur, CHNOPS), and of other key redox-sensitive elements that include iron (Fe), other first-row transition elements (FRTE), and cerium (Ce). As a result of these modifications, such evidence of Mars' life, paleoenvironmental history, potential habitability, and potential biosignatures would be corrupted or destroyed. Modifications of the abundances of some noble gases in samples heated during sterilization would also reset scientifically important radioisotope geochronometers and atmospheric-evolution measurements. Sterilization is designed to render terminally inactive (kill) all living microorganisms and inactivate complex biological structures (including bacterial spores, viruses, and prions). Sterilization processes do so by breaking certain pre-sterilization chemical bonds (including strong C-C, C-O, C-N, and C-H bonds of predominantly covalent character, as well as weaker hydrogen and van der Waals bonds) and forming different bonds and compounds, disabling the biological function of the pre-sterilization chemical compound. The group finds the following: No sterilization process could destroy the viability of cells whilst still retaining molecular structures completely intact. This applies not only to the organic molecules of living organisms, but also to most organic molecular biosignatures of former life (molecular fossils). As a matter of biological principle, any sterilization process would result in the loss of biological and paleobiological information, because this is the mechanism by which sterilization is achieved. Thus, almost all life science investigations would be compromised by sterilizing the subsample by either mode. Sterilization by dry heat at the proposed temperatures would lead to changes in many of the minerals and amorphous solids that are most significant for the study of paleoenvironments, habitability, potential biosignatures, and the geologic context of life-science observations. Gamma-(γ-)irradiation at even sub-MGy doses induces radiolysis of water. The radiolysis products (e.g., free radicals) react with redox-sensitive chemical species of interest for the study of paleoenvironments, habitability, and potential biosignatures, thereby adversely affecting measurements of those species. Heat sterilization and radiation also have a negative effect on CHNOPS and redox-sensitive elements. MSPG2 was unable to identify with confidence any measurement of abundances or oxidation-reduction states of CHNOPS elements, other redox-sensitive elements (e.g., Fe and other FRTE; Ce), or their isotopes that would be affected by only one, but not both, of the considered sterilization methods. Measurements of many attributes of volatile-rich subsamples are sterilization sensitive to both heat and γ-irradiation. Such a measurement is not useful to Mars science if what remains in the subsample is evidence of sterilization conditions and effects instead of evidence of conditions on Mars. Most measurements relating to the detection of evidence for extant or extinct life are sterilization sensitive. Many measurements other than those for life-science seek to retrieve Mars' paleoenvironmental information from the abundances or oxidation-reduction states of CHNOPS elements, other redox-sensitive elements, or their isotopes (and some noble gases) in returned samples. Such measurements inform scientific interpretations of (paleo)atmosphere composition and evolution, (paleo)surface water origin and chemical evolution, potential (paleo)habitability, (paleo)groundwater-porewater solute chemistry, origin and evolution, potential biosignature preservation, metabolic element or isotope fractionation, and the geologic, geochronological, and geomorphic context of life-sciences observations. Most such measurements are also sterilization sensitive. The sterilization-sensitive attributes cannot be meaningfully measured in any such subsample that has been sterilized by heat or γ-irradiation. Unless such subsamples are deemed biohazard-safe for release to external laboratories in unsterilized form, all such measurements must be made on unsterilized samples in biocontainment. An SRF should have the capability to carry out scientific investigations that are sterilization-sensitive to both PPO-provided sterilization methods (Figure SE1). The following findings have been recognized in the Report. Full explanations of the background, scope, and justification precede the presentation of each Finding in the Section identified for that Finding. One or more Findings follow our assessment of previous work on the effects of each provided sterilization method on each of three broad categories of measurement types—biosignatures of extant or ancient life, geological evidence of paleoenvironmental conditions, and gases. Findings are designated Major if they explicitly refer to both PPO-provided sterilization methods or have specific implications for the functionalities that need to be supported within an SRF. FINDING SS-1: More than half of the measurements described by iMOST for investigation into the presence of (mostly molecular) biosignatures (iMOST Objectives 2.1, 2.2 and 2.3) in returned martian samples are sterilization-sensitive and therefore cannot be performed with acceptable analytical precision or sensitivity on subsamples sterilized either by heat or by γ-irradiation at the sterilization parameters supplied to MSPG2. That proportion rises to 86% of the measurements specific to the investigation of extant or recent life (iMOST Objective 2.3) (see Section 2.5). This Finding supersedes Finding #4 of the MSPG Science in Containment report (MSPG, 2019). FINDING SS-2: Almost three quarters (115 out of 160; 72%) of the measurements described by iMOST for science investigations not associated with Objective 2 but associated with Objectives concerning geological phenomena that include past interactions with the hydrosphere (Objectives 1 and 3) and the atmosphere (Objective 4) are sterilization-tolerant and therefore can (generally) be performed with acceptable analytical precision or sensitivity on subsamples sterilized either by heat or by γ-irradiation at the sterilization parameters supplied to MSPG2 (see Section 2.5). This Finding supports Finding #6 of the MSPG Science in Containment report (MSPG, 2019).MSPG2 endorses the previously proposed strategy of conducting as many measurements as possible outside the SRF where the option exists. FINDING SS-3: Suggested strategies for investigating the potential for extant life in returned martian samples lie in understanding biosignatures and, more importantly, the presence of nucleic acid structures (DNA/RNA) and possible agnostic functionally similar information-bearing polymers. A crucial observation is that exposure of microorganisms to temperatures associated with sterilization above those typical of a habitable surface or subsurface environment results in a loss of biological information. If extant life is a target for subsample analysis, sterilization of material via dry heat would likely compromise any such analysis (see Section 3.2). FINDING SS-4: Suggested strategies for investigating the potential for extant life in returned martian samples lie in understanding biosignatures, including the presence of nucleic acid structures (DNA/RNA) and possible agnostic functionally similar information-bearing polymers. A crucial observation is that exposure of microorganisms to γ-radiation results in a loss of biological information through molecular damage and/or destruction. If extant life is a target for subsample analysis, sterilization of material via γ-radiation would likely compromise any such analysis (see Section 3.3). FINDING SS-5: Suggested strategies for investigating biomolecules in returned martian samples lie in detection of a variety of complex molecules, including peptides, proteins, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), as well as compounds associated with cell membranes such as lipids, sterols, and fatty acids and their geologically stable reaction products (hopanes, steranes, etc.) and possible agnostic functionally similar information-bearing polymers. Exposure to temperatures above MSR Campaign-Level Requirements for sample temperature, up to and including sterilization temperatures, results in a loss of biological information. If the presence of biosignatures is a target for subsample analysis, sterilization of material via dry heat would likely compromise any such analysis (see Section 4.2). FINDING SS-6: Suggested strategies for investigating biomolecules in returned martian samples lie in detection of a variety of complex molecules, including peptides, proteins, DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), and compounds associated with cell membranes such as lipids, sterols and fatty acids and their geologically stable reaction products (hopanes, steranes, etc.) and possible agnostic functionally similar information-bearing polymers. Exposure to radiation results in a loss of biological information. If the presence of biosignatures is a target for subsample analysis, sterilization of material via γ-irradiation would likely compromise any such analysis (see Section 4.3). FIG. SE1. A key SRF strategy is that the SRF is designed to initially accommodate only the measurements and analyses that cannot reasonably be made outside of biocontainment, including those required for initial sample characterization, Sample Safety Assessment Protocol (SSAP) tests, and time-sensitive science. Two scenarios are shown for sterilization-sensitive measurements that are contingent upon SSAP determination that sample is safe for unsterilized release (green YES path to uncontained outside laboratories) or unsafe for unsterilized release (red NO path to uncontained outside laboratories for sterilization tolerant science PLUS contained contingency laboratories enabling sterilization sensitive MSR Campaign measurements on unsterilized samples that cannot be deemed safe for release from containment). From Carrier et al. (2022). MAJOR FINDING SS-7: The use of heat or γ-irradiation sterilization should be avoided for subsamples intended to be used for organic biosignature investigations (for extinct or extant life). Studies of organic molecules from extinct or extant life (either indigenous or contaminants, viable or dead cells) or even some organic molecules derived from abiotic chemistry cannot credibly be done on subsamples that have been sterilized by any means. The concentrations of amino acids and other reduced organic biosignatures in the returned martian samples may also be so low that additional heat and/or γ-irradiation sterilization would reduce their concentrations to undetectable levels. It is a very high priority that these experiments be done on unsterilized subsamples inside containment (see Section 4.4). FINDING SS-8: Solvent extraction and acid hydrolysis at ∼100°C of unsterilized martian samples will inactivate any biopolymers in the extract and would not require additional heat or radiation treatment for the subsamples to be rendered sterile. Hydrolyzed extracts should be safe for analysis of soluble free organic molecules outside containment and may provide useful information about their origin for biohazard assessments; this type of approach, if approved, is strongly preferred and endorsed (see Section 4.4). FINDING SS-9: Minerals and amorphous materials formed by low temperature processes on Mars are highly sensitive to thermal alteration, which leads to irreversible changes in composition and/or structure when heated. Exposure to temperatures above MSR Campaign-Level Requirements for sample temperature, up to and including sterilization temperatures, has the potential to alter them from their as-received state. Sterilization by dry heat at the proposed sterilization temperatures would lead to changes in many of the minerals that are most significant for the study of paleoenvironments, habitability, and potential biosignatures or biosignature hosts. It is crucial that the returned samples are not heated to temperatures above which mineral transitions occur (see Section 5.3). FINDING SS-10: Crystal structure, major and non-volatile minor element abundances, and stoichiometric compositions of minerals are unaffected by γ-irradiation of up to 0.3–1 MGy, but crystal structures are completely destroyed at 130 MGy. Measurements of these specific properties cannot be acquired from subsamples γ-irradiated at the notional 1 MGy dose—they are sterilization-sensitive (see Section 5.4). FINDING SS-11: Sterilization by γ-irradiation (even at sub-MGy doses) results in significant changes to the redox state of elements bound within a mineral lattice. Redox-sensitive elements include Fe and other first-row transition elements (FRTE) as well as C, H, N, O, P and S. Almost all minerals and naturally occurring amorphous materials that formed under habitable conditions, including the ambient paleotemperatures of Mars' surface or shallow subsurface, contain at least one of these redox-sensitive elements. Therefore, measurements and investigations of the listed properties of such geological materials are sterilization sensitive and should not be performed on γ-irradiated subsamples (see Section 5.4). FINDING SS-12: A significant fraction of investigations that focus on high-temperature magmatic and impact-related processes, their chronology, and the chronology of Mars' geophysical evolution are sterilization-tolerant. While there may be a few analyses involved in such investigations that could be affected to some degree by heat sterilization, most of these analyses would not be affected by sterilization involving γ-irradiation (see Section 5.6). MAJOR FINDING SS-13: Scientific investigations of materials containing hydrous or otherwise volatile-rich minerals and/or X-ray amorphous materials that formed or were naturally modified at low (Mars surface-/near-surface) temperature are sterilization-sensitive in that they would be compromised by changes in the abundances, redox states, and isotopes of CHNOPS and other volatiles (e.g., noble gases for chronometry), FRTE, and Ce, and cannot be performed on subsamples that have been sterilized by either dry heat or γ-irradiation (see Section 5.7). MAJOR FINDING SS-14: It would be far preferable to work on sterilized gas samples outside of containment, if the technical issues can all be worked out, than to build and operate a large gas chemistry laboratory inside containment. Depending on their reactivity (or inertness), gases extracted from sample tubes could be sterilized by dry heat or γ-irradiation and analyzed outside containment. Alternatively, gas samples could be filtered through an inert grid and the filtered gas analyzed outside containment (see Section 6.5). MAJOR FINDING SS-15: It is fundamental to the campaign-level science objectives of the Mars Sample Return Campaign that the SRF support characterization of samples returned from Mars that contain organic matter and/or minerals formed under habitable conditions that include the ambient paleotemperatures of Mars' surface or subsurface (<∼200°C)—such as most clays, sulfates, and carbonates—in laboratories on Earth in their as-received-at-the-SRF condition (see Section 7.1). MAJOR FINDING SS-16: The search for any category of potential biosignature would be adversely affected by either of the proposed sterilization methods (see Section 7.1). MAJOR FINDING SS-17: Carbon, hydrogen, nitrogen, oxygen, sulfur, phosphorus, and other volatiles would be released from a subsample during the sterilization step. The heat and γ-ray sterilization chambers should be able to monitor weight loss from the subsample during sterilization. Any gases produced in the sample headspace and sterilization chamber during sterilization should be captured and contained for future analyses of the chemical and stable isotopic compositions of the evolved elements and compounds for all sterilized subsamples to characterize and document fully any sterilization-induced alteration and thereby recover some important information that would otherwise be lost (see Section 7.2). This report shows that most of the sterilization-sensitive iMOST measurement types are among either the iMOST objectives for life detection and life characterization (half or more of the measurements for life-science sub-objectives are critically sterilization sensitive) or the iMOST objectives for inferring paleoenvironments, habitability, preservation of potential biosignatures, and the geologic context of life-science observations (nearly half of the measurements for sub-objectives involving geological environments, habitability, potential biosignature preservation, and gases/volatiles are critically sterilization sensitive) (Table 2; see Beaty et al.,2019 for the full lists of iMOST objectives, goals, investigations, and sample measurement types). Sterilization-sensitive science about ancient life on Mars and its relationship to its ancient environment will be severely impaired or lost if the samples collected by Perseverance cannot be analyzed in an unsterilized condition. Summary: ○ The SRF should have the capability to carry out or otherwise support scientific investigations that are sensitive to both PPO-provided sterilization methods. ○ Measurements of most life-sciences and habitability-related (paleoenvironmental) phenomena are sensitive to both PPO-provided sterilization modes. (Major Finding SS-7, SS-15, SS-16 and Finding SS-1, SS-3, SS-4, SS-5, SS-6, SS-9, SS-11, SS-13) If subsamples for sterilization-sensitive measurement cannot be deemed safe for release, then additional contingency analytical capabilities are needed in the SRF to complete MSR Campaign measurements of sterilization-sensitive sample properties on unsterilized samples in containment (Figure SE1, below). ○ Measurements of high-temperature (low-volatile) phenomena are tolerant of both PPO-provided sterilization modes (Finding SS-12). Subsamples for such measurements may be sterilized and released to laboratories outside containment without compromising the scientific value of the measurements. ○ Capturing, transporting, and analyzing gases is important and will require careful design of apparatus. Doing so for volatiles present as headspace gases and a dedicated atmosphere sample will enable important atmospheric science (Major Finding SS-14). Similarly, capturing and analyzing gases evolved during subsample sterilization (i.e., gas from the sterilization chamber) would compensate for some sterilization-induced loss of science data from volatile-rich solid (geological) subsamples (Finding SS-14, SS-17; other options incl. SS-8). [ABSTRACT FROM AUTHOR]
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- 2022
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4. Recommendation on Orbiting Sample Cleanliness.
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Cockell, Charles S., Chitale, Rohit, Clement, Brian, Davila, Alfonso, Freeman, Katherine H., French, Katherine L., Glavin, Daniel P., Hays, Lindsay E., Hummel, Kimberly, Meyer, Michael A., Pratt, Lisa M., Salvo, Christopher, Seasly, Elaine, and Tsang, Kar Wing
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HYGIENE , *ORBITS (Astronomy) , *BACTERIAL spores , *MARS (Planet) , *SPACE research - Abstract
The National Aeronautics and Space Administration-European Space Agency (NASA-ESA) Mars Sample Return (MSR) campaign involves the collection of samples on Mars by the Perseverance (Mars 2020) rover and their return to Earth. To accomplish this, the Orbiting Sample container (OS) will be sent to Mars to accommodate the collected samples then launched from Mars and returned to Earth, where the samples will be removed for examination in the Sample Return Facility (SRF). Crucial to this entire sequence will be establishment of the required level of cleanliness inside the OS. In February 2021, the NASA Headquarters' Mars Sample Return Program and Office of Planetary Protection assembled an MSR OS Tiger Team (OSTT) to discuss the appropriate cleanliness level options of the interior of the OS. The team's remit was primarily focused on evaluating the trade-offs between Planetary Protection cleanliness levels 4a and 4b. These cleanliness levels are determined by the Committee on Space Research (COSPAR) planetary protection regulations, where 4a requires <300 bacterial spores/m2 and <3 x 105 bacterial spores on the spacecraft (in this case, the interior of the OS) and 4b mandates the more stringent requirement of <30 bacterial spores on the spacecraft. This report documents the consensus opinion submitted by the OSTT that recommended the interior of the OS be cleaned to a 4a requirement with any feasible added effort toward 4b. This report provides, as well, the rationale for that decision. [ABSTRACT FROM AUTHOR]
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- 2022
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5. Planning the Human Future Beyond Earth with the Prison Population: The Life Beyond Project.
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Cockell, Charles S., Perera, Liam, and Bass, Rachel
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PRISON population , *PRISON conditions , *SPACE environment , *SPACE exploration , *HUMAN settlements - Abstract
Prisons are in some significant respects similar to planetary stations. Their occupants live within a social environment that is confined, takes on its own culture with a strong interdependence and camaraderie between individuals, and contains within it huge latent talents in art, science, engineering, and other disciplines. Recognizing this potential, the Life Beyond project involves the prison population in designing settlements for the Moon and Mars. Involving ∼160 prisoners in Scotland, the project has led to two published books presenting strategies for the settlement of the Moon and Mars. Building on this, a set of course materials was devised for any prisoner anywhere to contribute ideas and plans for the human exploration and settlement of space. Here, we describe this project, the methods used, and the results. In addition to improving educational opportunities in prisons through space science and elements of astrobiology, the project demonstrates the potential for prisoners to contribute to space settlement by applying their experience of the prison space analog environment. [ABSTRACT FROM AUTHOR]
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- 2021
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6. Biologically Available Chemical Energy in the Temperate but Uninhabitable Venusian Cloud Layer: What Do We Want to Know?
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Cockell, Charles S., Higgins, Peter M., and Johnstone, Andrew A.
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CHEMICAL energy , *CLOUD droplets , *HYDROGEN oxidation , *VENUS (Planet) , *PLANETARY atmospheres , *ELECTRON donors , *SULFUR cycle - Abstract
The cloud layer has been hypothesized to be the most habitable region of Venus. In the lower clouds, both temperature and pressure fall within bounds that support reproduction of microbial life on Earth, although the water activity of the sulfuric acid cloud droplets makes the clouds uninhabitable to known life. In this study, we carried out an analysis of CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, sulfur) elements and potential redox couples in the cloud layer, and we used a microbial energetic growth model to investigate quantitatively the chemical energy available for microbial growth from methanogenesis, sulfate reduction, and hydrogen oxidation at temperatures between 278 and 350 K. The purpose was to improve knowledge of how far the venusian cloud layer comes from being habitable. Hydrogen oxidation was favorable at all temperatures; however, negative Gibbs free energies for sulfate reduction and methanogenesis depended critically on the assumed concentrations of electron donors, acceptors, and products. Improved measurements and the investigation of new molecules will allow us to better assess quantitatively how far Venus comes from possessing a habitable cloud layer and what would need to be different to make it habitable. We identify specific required measurements. These data will advance our understanding of the habitability of planetary atmospheres on extrasolar greenhouse worlds and the habitability of Earth when the planet eventually enters a greenhouse state. [ABSTRACT FROM AUTHOR]
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- 2021
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7. Minimum Units of Habitability and Their Abundance in the Universe.
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Cockell, Charles S., Wordsworth, Robin, Whiteford, Niall, and Higgins, Peter M.
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MAXIMA & minima , *EXTRASOLAR planets , *CHARTS, diagrams, etc. , *HYPOTHESIS ,UNIVERSE - Abstract
Although the search for habitability is a much-vaunted objective in the study of planetary environments, the material requirements for an environment to be habitable can be met with relatively few ingredients. In this hypothesis paper, the minimum material requirements for habitability are first re-evaluated, necessarily based on life "as we know it." From this vantage point, we explore examples of the minimum number of material requirements for habitable conditions to arise in a planetary environment, which we illustrate with "minimum habitability diagrams." These requirements raise the hypothesis that habitable conditions may be common throughout the universe. If the hypothesis was accepted, then the discovery of life would remain an important discovery, but habitable conditions on their own would be an unremarkable feature of the material universe. We discuss how minimum units of habitability provide a parsimonious way to consider the minimum number of geological inferences about a planetary body, and the minimum number of atmospheric components that must be measured, for example in the case of exoplanets, to be able to make assessments of habitability. [ABSTRACT FROM AUTHOR]
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- 2021
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8. The Biological Study of Lifeless Worlds and Environments.
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Cockell, Charles S.
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ORIGIN of life , *ASTROBIOLOGY , *MICROORGANISMS , *PHYSICAL training & conditioning , *PLANETARY science ,UNIVERSE - Abstract
Astrobiology is focused on the study of life in the universe. However, lifeless planetary environments yield biological information on the variety of ways in which physical and chemical conditions in the universe preclude the possibility of the origin or persistence of life, and in turn this will help explain the distribution and abundance of life, or lack of it, in the universe. Furthermore, many places that humans wish to explore and settle in space are lifeless, and studying the fate of life in these environments will aid our own success in thriving in them. In this synthetic review, I have three objectives, as follows: (1) To discuss the biological value and use of lifeless environments, (2) To explore the diverse planetary bodies and environments that can be lifeless and to categorize them, and (3) To propose sets of biological experiments that can be undertaken in different categories of lifeless worlds and environments and suggest concepts for mission ideas to realize these goals. They include origin of life and microbial inoculation experiments in lifeless but habitable environments. I suggest that the biological study of lifelessness is an underappreciated area in planetary sciences. [ABSTRACT FROM AUTHOR]
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- 2021
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9. Perchlorate Salts Exert a Dominant, Deleterious Effect on the Structure, Stability, and Activity of α-Chymotrypsin.
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Gault, Stewart and Cockell, Charles S.
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SALTS , *LIFE on Mars , *SALT , *MARS (Planet) , *IONS - Abstract
The presence of perchlorate ions on Mars raises the question of how these ions influence the biochemistry of any contaminant life introduced into the martian environment, or what selection pressures perchlorate ions exert on any environment that contains these ions, such as the Atacama Desert. In this study, we investigated the structure, stability, and enzyme activity of the model enzyme α-chymotrypsin in the presence of five Mars relevant salts, MgSO4, MgCl2, Mg(ClO4)2, Ca(ClO4)2, and NaClO4. We found that all the perchlorate salts reduced the enzyme activity of α-chymotrypsin in a concentration-dependent manner, with Mg(ClO4)2 and Ca(ClO4)2 having the greatest effect. This observation extends to our structural studies, which show that 1 M Mg(ClO4)2 and Ca(ClO4)2 greatly alter the tertiary structural environment of α-chymotrypsin. We also found that all the perchlorate salts assayed reduced the melting temperature of α-chymotrypsin, whereas the sulfate and chloride salts were able to increase the protein melting temperature. We also demonstrated that a brine containing both perchlorate and sulfate ions exerts the same deleterious effects on α-chymotrypsin's melting temperature and enzyme activity as that of a perchlorate-only brine. This suggests that the perchlorate salts exert a dominant, deleterious effect on protein biochemistry. These results indicate that although perchlorate salts are beneficial to the presence of liquid water due to low eutectic points, they also hamper the habitability of their own environment. Life in such brines would, therefore, have to adapt its cellular machinery to the perchlorate ion's presence or find a way of excluding it from said machinery. [ABSTRACT FROM AUTHOR]
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- 2021
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10. Preservation of Bacillus subtilis' cellular liquid state at deep sub-zero temperatures in perchlorate brines.
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Gault, Stewart, Fonseca, Fernanda, and Cockell, Charles S.
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DIFFERENTIAL scanning calorimetry , *BACILLUS subtilis , *LOW temperatures , *SALT , *UNICELLULAR organisms , *VITRIFICATION - Abstract
Although a low temperature limit for life has not been established, it is thought that there exists a physical limit imposed by the onset of intracellular vitrification, typically occurring at ~−20 °C for unicellular organisms. Here, we show, through differential scanning calorimetry, that molar concentrations of magnesium perchlorate can depress the intracellular vitrification point of Bacillus subtilis cells to temperatures much lower than those previously reported. At 2.5 M Mg(ClO4)2, the peak vitrification temperature was lowered to −83 °C. Our results show that inorganic eutectic salts can in principle maintain liquid water in cells at much lower temperatures than those previously claimed as a lower limit to life, raising the prospects of active biochemical processes in low temperature natural settings. Our results may have implications for the habitability of Mars, where perchlorate salts are pervasive and potentially other terrestrial and extraterrestrial, cryosphere environments. A differential scanning calorimetry study of Bacillus subtilis vitrification shows that perchlorate salts can lower the onset of intracellular vitrification, with implications for the low temperature limit of life in salt-rich subzero environments. [ABSTRACT FROM AUTHOR]
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- 2024
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11. When is Life a Viable Hypothesis? The Case of Venusian Phosphine.
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Cockell, Charles S., McMahon, Sean, and Biddle, Jennifer F.
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- 2021
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12. Growth of Non-Halophilic Bacteria in the Sodium–Magnesium–Sulfate–Chloride Ion System: Unravelling the Complexities of Ion Interactions in Terrestrial and Extraterrestrial Aqueous Environments.
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Cockell, Charles S., McLean, Claire-Marie, Perera, Liam, Aka, Salomé, Stevens, Adam, and Dickinson, Andrew W.
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SPACE environment , *CHLORIDE ions , *IONIC strength , *BODIES of water , *IONS , *BACTERIA - Abstract
Motivated by an interest in understanding the habitability of aqueous environments on Earth and in extraterrestrial settings, this study investigated the influence of ions in an artificial sodium–magnesium–sulfate–chloride ion system on the growth parameters (lag phase, growth rate, and final cell concentration) of bacteria. These four ions, in different combinations, are key components of many aqueous environments on Earth and elsewhere. We investigated non-halophilic bacteria deliberately to remove the bias of prior adaptations to high concentrations of selected ions so that we could compare the effects of different ions. We tested the hypothesis that water activity determined the growth parameters independent of the ion types. Neither water activity or ionic strength alone could predict growth. However, when ionic strengths were matched, many differences in growth parameters could be explained by the water activity. We suggest that species-specific effects (caused by differences in biochemical and physiological influences), the role of individual ions in cellular processes, and potentially the chaotropicity and kosmotropicity of solutions influenced the growth. Our data show that although extreme combinations of these ions allow for general predictions on the habitability of extraterrestrial aqueous environments, a complex interplay of ionic effects influences the growth and thus the adaptations required for given ion combinations. The data also show that an accurate quantification of the habitability of ocean worlds, such as Europa and Enceladus, can only be made when samples are obtained from these water bodies and the ion combinations are determined. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
13. 0.25 Ga Salt Deposits Preserve Signatures of Habitable Conditions and Ancient Lipids.
- Author
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Cockell, Charles S., Wilhelm, Mary Beth, Perl, Scott, Wadsworth, Jennifer, Payler, Sam, McMahon, Sean, Paling, Sean, and Edwards, Thomas
- Subjects
- *
SALT deposits , *EVAPORITES , *LIPIDS , *STRONTIUM isotopes , *QUARTZ , *POLYGONS - Abstract
Polygonal features in a ∼250 million-year-old Permian evaporitic deposit were investigated for their geological and organic content to test the hypothesis that they could preserve the signature of ancient habitable conditions and biological activity. Investigations on evaporitic rock were carried out as part of the MIne Analog Research (MINAR) project at Boulby Mine, the United Kingdom. The edges of the polygons have a higher clay content and contain higher abundances of minerals such as quartz and microcline, and clays such as illite and chlorite, compared with the interior of polygons, suggesting that the edges were preferred locations for the accumulation of weathering products during their formation. The mineral content and its strontium isotope ratio suggest that the material is from continental weathering at the borders of the Permian Zechstein Sea. The edges of the polygons contain material with mean δ13C and δ15N values of −20.8 and 5.3, respectively. Lipids, including alkanes and hopanes, were extracted from the interior and edges of the polygons, which are inferred to represent organic material entrained in the evaporites when they were formed. The presence of long-chain alkanes (C20–C35) that lack a carbon preference, low abundances of C23–C29 hopanes, and lack of marine, evaporitic, or thermal maturity indicators show that lipid biomarkers were, at least in part, potentially derived from a continental source and have not undergone significant thermal maturation since deposition. Lipid extractions using weak acids revealed significantly more lipids than those without acid, potentially indicating that encapsulation was not the only type of preservation mechanism occurring in Boulby salts. These data demonstrate the potential for ancient evaporites and their polygons to preserve information on local geological conditions, ancient habitability, and evidence of life. The data show that analogous martian evaporitic deposits are good targets for future life detection missions and the investigation of ancient martian habitability. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
14. Persistence of Habitable, but Uninhabited, Aqueous Solutions and the Application to Extraterrestrial Environments.
- Author
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Cockell, Charles S.
- Subjects
- *
SPACE environment , *AQUEOUS solutions , *ELECTRON donors , *BODIES of water , *EXTREME environments , *PHOSPHORUS cycle (Biogeochemistry) - Abstract
In most environments on Earth, habitable environments contain life. Experiments were conducted to investigate the decoupling of the presence of habitable conditions and life. A set of microcosms habitable for known groups of organisms, but uninhabited (i.e., uninhabited habitats), was exposed to external environmental conditions to test the hypothesis that extreme habitable environments can remain uninhabited for sustained time periods. These microcosms were made of tubes containing liquid water and inorganic N, P, and S. Organics (used as electron donors and as a C source) were provided as L and D amino acids. One set of uninhabited habitats contained no additional salts, one set contained saturated NaCl, and one set contained saturated MgSO4. A ddH2O control and a complex medium for Halobacterium were used as controls. The presence of organisms was tested by enumeration of colonists and sequencing of extracted DNA. At each time point, inoculation into fresh medium was used to test for growth of organisms. After 1 week, the "no salt" and saturated MgSO4 solutions were colonized. After 6 months, both the NaCl-saturated and Halobacterium solutions remained uninhabited, but all other samples were colonized. These experiments demonstrate that certain types of habitable liquid water environments exposed to microbial atmospheric inoculation, even on Earth, can remain devoid of reproducing life for many months. On other planetary bodies, such as Mars, these data imply the possibility of preserved transient water bodies that would record habitable conditions, but no evidence of life, even if life existed elsewhere on the planet. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
15. Effects of rapid depressurisation on the structural integrity of common foodstuffs.
- Author
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Cockell, Charles S. and McLaughlin, Scott
- Subjects
- *
FLUID foods , *FOOD storage , *RAW foods , *ATMOSPHERIC pressure , *WRINKLES (Skin) , *FRUIT , *PREPARED foods - Abstract
In preparation for the eventual manufacture and storage of food in space, we conducted a set of experiments to determine the effect of a rapid catastrophic depressurisation on a range of common foodstuffs. The experiment tested the hypothesis that rapid depressurisation would cause explosive destruction or boiling of stored foodstuffs. We tested 18 types of fruit, 18 types of vegetables, 4 types of nuts, 4 types of fish, 10 types of raw and prepared meat, chicken eggs, 9 types of cheese and 8 other foods including rice and lentils. They were exposed to depressurisation from atmospheric pressure to 6 mb in 5.67 min to simulate a rapid depressurisation event on Mars. We found most of the tested produce to be robust against depressurisation. No explosive rupture or failure was observed in any of the tested items. Introduction of cuts into the produce resulted in localised bubbling, for example in tomatoes, and bubbling was observed at the site of bruising, for example in bananas and pears. At pressures greater than ∼30 mb we attribute this to outgassing and below this pressure to a combination of outgassing and boiling and we present a general model to describe these findings. Raw meat (such as ham), fish (such as salmon) and some cheeses (such as Mozzarella) bubbled at their surfaces, causing the surface to dry. The most profound changes were observed in sausages, haggis and chicken in which air expanded beneath the skins, stretching the skin and causing wrinkling when repressurisation occurred, although the overall integrity of the food was not altered. We conclude that a rapid depressurisation event in a food storage unit would not cause catastrophic physical disruption of food. However, secondary protection inside closed containers is advisable for fish, raw and prepared meats, fruits and vegetables with observable bruising or damage, to protect against drying during a depressurisation event. Our data show the potential for low pressure storage of food. • Observations on the effects of rapid depressurisation on common foodstuffs. • Demonstration that no foodstuffs showed catastrophic loss of structural integrity on rapid depressurisation. • Discussion on generalised model for understanding effects of depressurisation on foods and behaviour of food fluids. • Discussion on further areas of research on food storage in space. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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- View/download PDF
16. The minimum energy required to build a cell.
- Author
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Ortega-Arzola, Edwin, Higgins, Peter M., and Cockell, Charles S.
- Abstract
Understanding the energy requirements for cell synthesis accurately and comprehensively has been a longstanding challenge. We introduce a computational model that estimates the minimum energy necessary to build any cell from its constituent parts. This method combines omics and internal cell compositions from various sources to calculate the Gibbs Free Energy of biosynthesis independently of specific metabolic pathways. Our public tool, Synercell, can be used with other models for minumum species-specific energy estimations in any well-sequenced species. The energy for synthesising the genome, transcriptome, proteome, and lipid bilayer of four cell types: Escherichia coli, Saccharomyces cerevisiae, an average mammalian cell and JCVI-syn3A were estimated. Their modelled minimum synthesis energies at 298 K were 9.54 × 10 - 11 J/cell, 4.99 × 10 - 9 J/cell, 3.71 × 10 - 7 J/cell and 3.69 × 10 - 12 respectively. Gram-for-gram synthesis of lipid bilayers requires the most energy, followed by the proteome, genome, and transcriptome. The average per gram cost of biomass synthesis is in the 300s of J/g for all four cells. Implications for the generalisability of cell construction and applications to biogeosciences, cellular biology, biotechnology, and astrobiology are discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
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17. A Low-Diversity Microbiota Inhabits Extreme Terrestrial Basaltic Terrains and Their Fumaroles: Implications for the Exploration of Mars.
- Author
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Cockell, Charles S., Harrison, Jesse P., Stevens, Adam H., Payler, Samuel J., Hughes, Scott S., Kobs Nawotniak, Shannon E., Brady, Allyson L., Elphic, R.C., Haberle, Christopher W., Sehlke, Alexander, Beaton, Kara H., Abercromby, Andrew F.J., Schwendner, Petra, Wadsworth, Jennifer, Landenmark, Hanna, Cane, Rosie, Dickinson, Andrew W., Nicholson, Natasha, Perera, Liam, and Lim, Darlene S.S.
- Subjects
- *
BASALT , *MARS (Planet) , *MICROBIAL diversity , *PLANETARY exploration , *TERRAIN mapping - Abstract
A major objective in the exploration of Mars is to test the hypothesis that the planet hosted life. Even in the absence of life, the mapping of habitable and uninhabitable environments is an essential task in developing a complete understanding of the geological and aqueous history of Mars and, as a consequence, understanding what factors caused Earth to take a different trajectory of biological potential. We carried out the aseptic collection of samples and comparison of the bacterial and archaeal communities associated with basaltic fumaroles and rocks of varying weathering states in Hawai'i to test four hypotheses concerning the diversity of life in these environments. Using high-throughput sequencing, we found that all these materials are inhabited by a low-diversity biota. Multivariate analyses of bacterial community data showed a clear separation between sites that have active fumaroles and other sites that comprised relict fumaroles, unaltered, and syn-emplacement basalts. Contrary to our hypothesis that high water flow environments, such as fumaroles with active mineral leaching, would be sites of high biological diversity, alpha diversity was lower in active fumaroles compared to relict or nonfumarolic sites, potentially due to high-temperature constraints on microbial diversity in fumarolic sites. A comparison of these data with communities inhabiting unaltered and weathered basaltic rocks in Idaho suggests that bacterial taxon composition of basaltic materials varies between sites, although the archaeal communities were similar in Hawai'i and Idaho. The taxa present in both sites suggest that most of them obtain organic carbon compounds from the atmosphere and from phototrophs and that some of them, including archaeal taxa, cycle fixed nitrogen. The low diversity shows that, on Earth, extreme basaltic terrains are environments on the edge of sustaining life with implications for the biological potential of similar environments on Mars and their exploration by robots and humans. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
18. Life Beyond--A Program to Use Astrobiology to Teach Science and Advance Space Exploration Through Prisons.
- Author
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Cockell, Charles S., Gutierrez Fosado, Yair Augusto, Hitchen, James, Landenmark, Hanna, Perera, Liam, and Vissers, Teun
- Subjects
- *
EDUCATION of prisoners , *SPACE biology , *SPACE exploration , *SCIENCE education , *JUVENILE corrections ,STUDY & teaching - Abstract
The field of astrobiology is concerned with the origin, evolution, and distribution of life in the Universe. It contains within it civilization-level questions such as: What is the future of humanity on Earth and can we successfully explore and settle other planets? As such, it offers an educational framework for both teaching basic science and for engaging individuals in questions about how society can take on its biggest challenges and opportunities. Life Beyond is a collaboration between the UK Centre for Astrobiology and the Scottish Prison Service (SPS) to take astrobiology into the prison environment. Using a pilot program across four Scottish prisons, a 4-week astrobiology course focused on designing a station for Mars was developed. Learning outcomes ranged from improvements in literacy, numeracy, and science skills to enhancing civic responsibilities. The results of the initiative are products such as Mars station designs, essays, and art, providing participants with tangible outputs. We describe the pilot initiative, the 4-week Life Beyond course, and draw conclusions about the use of astrobiology as a vehicle for teaching science and advancing social reform in the prison environment. [ABSTRACT FROM AUTHOR]
- Published
- 2018
19. The UK Centre for Astrobiology: A Virtual Astrobiology Centre. Accomplishments and Lessons Learned, 2011-2016.
- Author
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Cockell, Charles S., Biller, Beth, Bryce, Casey, Cousins, Claire, Direito, Susana, Forgan, Duncan, Fox-Powell, Mark, Harrison, Jesse, Landenmark, Hanna, Nixon, Sophie, Payler, Samuel J., Rice, Ken, Samuels, Toby, Schwendner, Petra, Stevens, Adam, Nicholson, Natasha, and Wadsworth, Jennifer
- Subjects
- *
ASTROBIOLOGY , *EXTREME environments , *EXTRATERRESTRIAL life , *ASTRONOMY , *EARTH sciences - Abstract
The UK Centre for Astrobiology (UKCA) was set up in 2011 as a virtual center to contribute to astrobiology research, education, and outreach. After 5 years, we describe this center and its work in each of these areas. Its research has focused on studying life in extreme environments, the limits of life on Earth, and implications for habitability elsewhere. Among its research infrastructure projects, UKCA has assembled an underground astrobiology laboratory that has hosted a deep subsurface planetary analog program, and it has developed new flow-through systems to study extraterrestrial aqueous environments. UKCA has used this research backdrop to develop education programs in astrobiology, including a massive open online course in astrobiology that has attracted over 120,000 students, a teacher training program, and an initiative to take astrobiology into prisons. In this paper, we review these activities and others with a particular focus on providing lessons to others who may consider setting up an astrobiology center, institute, or science facility. We discuss experience in integrating astrobiology research into teaching and education activities. Key Words: Astrobiology-Centre-Education-Subsurface-Analog research. Astrobiology 18, 224-243. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
20. The Janus face of iron on anoxic worlds: iron oxides are both protective and destructive to life on the early Earth and present-day Mars.
- Author
-
Wadsworth, Jennifer and Cockell, Charles S.
- Subjects
- *
ULTRAVIOLET radiation , *DNA damage , *FERRIC oxide , *BACILLUS subtilis , *HEMATITE - Abstract
The surface of the early Earth was probably subjected to a higher flux of ultraviolet (UV) radiation than today. UV radiation is known to severely damage DNA and other key molecules of life. Using a liquid culture and a rock analogue system, we investigated the interplay of protective and deleterious effects of iron oxides under UV radiation on the viability of the model organism, Bacillus subtilis. In the presence of hydrogen peroxide, there exists a fine balance between iron oxide's protective effects against this radiation and its deleterious effects caused by Photo-Fenton reactions. The maximum damage was caused by a concentration of hematite of ~1 mg/mL. Concentrations above this confer increasing protection by physical blockage of the UV radiation, concentrations below this cause less effective UV radiation blockage, but also a correspondingly less effective Photo-Fenton reaction, providing an overall advantage. These results show that on anoxic worlds, surface habitability under a high UV flux leaves life precariously poised between the beneficial and deleterious effects of iron oxides. These results have relevance to the Archean Earth, but also the habitability of the Martian surface, where high levels of UV radiation in combination with iron oxides and hydrogen peroxide can be found. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
21. Liquid Water Restricts Habitability in Extreme Deserts.
- Author
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Cockell, Charles S., Brown, Sarah, Landenmark, Hanna, Samuels, Toby, Siddall, Rebecca, and Wadsworth, Jennifer
- Subjects
- *
DESERT ecology , *MICROBIOLOGY of extreme environments , *HABITATS , *PHOTOSYNTHETIC bacteria , *ASTROBIOLOGY - Abstract
Liquid water is a requirement for biochemistry, yet under some circumstances it is deleterious to life. Here, we show that liquid water reduces the upper temperature survival limit for two extremophilic photosynthetic microorganisms ( Gloeocapsa and Chroococcidiopsis spp.) by greater than 40°C under hydrated conditions compared to desiccated conditions. Under hydrated conditions, thermal stress causes protein inactivation as shown by the fluorescein diacetate assay. The presence of water was also found to enhance the deleterious effects of freeze-thaw in Chroococcidiopsis sp. In the presence of water, short-wavelength UV radiation more effectively kills Gloeocapsa sp. colonies, which we hypothesize is caused by factors including the greater penetration of UV radiation into hydrated colonies compared to desiccated colonies. The data predict that deserts where maximum thermal stress or irradiation occurs in conjunction with the presence of liquid water may be less habitable to some organisms than more extreme arid deserts where organisms can dehydrate prior to being exposed to these extremes, thus minimizing thermal and radiation damage. Life in extreme deserts is poised between the deleterious effects of the presence and the lack of liquid water. Key Words: Deserts-Extremophiles-Stress-High temperatures-UV radiation-Desiccation. Astrobiology 17, 309-318. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
22. The laws of life.
- Author
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Cockell, Charles S.
- Subjects
- *
LIFE (Biology) , *BIOSPHERE , *ORGANISMS , *LIFE sciences , *PHYSICAL laws - Abstract
The article offers information related to the study of life such as the laws and principle concerning the diversity of living creatures as well as the forms and processes of life. Several topics being mentioned include Earth's evolutionary experiment, physical laws, and complex multicellular biosphere.
- Published
- 2017
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- View/download PDF
23. An ESA roadmap for geobiology in space exploration.
- Author
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Cousins, Claire R and Cockell, Charles S
- Subjects
- *
GEOBIOLOGY , *BIOSIGNATURES (Origin of life) , *LIFE support systems in critical care , *SPACE exploration - Abstract
Geobiology, and in particular mineral–microbe interactions, has a significant role to play in current and future space exploration. This includes the search for biosignatures in extraterrestrial environments, and the human exploration of space. Microorganisms can be exploited to advance such exploration, such as through biomining, maintenance of life-support systems, and testing of life-detection instrumentation. In view of these potential applications, a European Space Agency (ESA) Topical Team “Geobiology in Space Exploration” was developed to explore these applications, and identify research avenues to be investigated to support this endeavour. Through community workshops, a roadmap was produced, with which to define future research directions via a set of 15 recommendations spanning three key areas: Science, Technology, and Community. These roadmap recommendations identify the need for research into: (1) new terrestrial space-analogue environments; (2) community level microbial–mineral interactions; (3) response of biofilms to the space environment; (4) enzymatic and biochemical mineral interaction; (5) technical refinement of instrumentation for space-based microbiology experiments, including precursor flight tests; (6) integration of existing ground-based planetary simulation facilities; (7) integration of fieldsite biogeography with laboratory- and field-based research; (8) modification of existing planetary instruments for new geobiological investigations; (9) development of in situ sample preparation techniques; (10) miniaturisation of existing analytical methods, such as DNA sequencing technology; (11) new sensor technology to analyse chemical interaction in small volume samples; (12) development of reusable Lunar and Near Earth Object experimental platforms; (13) utility of Earth-based research to enable the realistic pursuit of extraterrestrial biosignatures; (14) terrestrial benefits and technological spin-off from existing and future space-based geobiology investigations; and (15) new communication avenues between space agencies and terrestrial research organisations to enable this impact to be developed. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
24. Detecting Microbiology in the Upper Atmosphere: Relative-Velocity Filtered Sampling.
- Author
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Berera, Arjun, Brener, Daniel J., and Cockell, Charles S.
- Subjects
- *
UPPER atmosphere , *THERMOSPHERE , *MICROBIOLOGY , *BIOMATERIALS , *RELATIVE velocity , *MESOSPHERE - Abstract
The purpose of this article is to reopen from a practical perspective the question of the extent in altitude of Earth's biosphere. We make a number of different suggestions for how searches for biological material could be conducted in the mesosphere and lower thermosphere, colloquially referred to as the "ignore-osphere" because it has been generally ignored in the meteorological community compared to other regions. Relatively recent technological advances such as CubeSats in very low Earth orbit or more standard approaches such as the rocket-borne MAGIC meteoric smoke particle sampler are shown as potentially viable for sampling biological material in the ignore-osphere. The issue of contamination is discussed, and a potential solution to the problem is proposed by means of a new detector design that filters for particles based on their size and relative velocity to the detector. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
25. The Interlayer Regions of Sheet Silicates as a Favorable Habitat for Endolithic Microorganisms.
- Author
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Kapitulčinová, Dana, Cockell, Charles S., Patel, Manish, and Ragnarsdóttir, Kristín Vala
- Subjects
- *
PHOTOSYNTHETIC bacteria , *ECOLOGICAL niche , *BIOTITE , *MICROORGANISMS , *CYANOBACTERIA - Abstract
Dark-colored rocks that attenuate photosynthetically active radiation (PAR) are generally thought to be poor substrates for endolithic colonization. In this study we show that the internal space of the common dark-colored mica mineral, biotite, is a favorable microhabitat for the growth of filamentous cyanobacteria. Laboratory incubation experiments demonstrated that filamentous cyanobacteria with a cell diameter of ≤3 μm were able to colonize biotite interlayers. Light transmittance measurements on solid biotite sheets showed that PAR (400–690 nm) transmission is sufficient to allow for cyanobacterial growth in the interlayer regions of the mineral. Of note is that damaging UV radiation is attenuated by more than one order of magnitude at the corresponding depth, most likely by the iron contained within the mineral, showing that the interlayer region represents a UV protected microhabitat with respect to the mineral surface. The interlayer region is therefore a favorable environment for small cells that cannot rely only on UV screening compounds. These results show that biotite, and by extension other layered silicate minerals, are a hitherto unrecognized habitat suitable for endolithic microorganisms with potential implications in research fields such as astrobiology. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
26. Nonphotosynthetic Pigments as Potential Biosignatures.
- Author
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Schwieterman, Edward W., Cockell, Charles S., and Meadows, Victoria S.
- Subjects
- *
PHOTOSYNTHETIC pigments , *BIOSIGNATURES (Origin of life) , *PHOTOSYNTHESIS , *EXTRASOLAR planets , *HALOPHILIC microorganisms - Abstract
Previous work on possible surface reflectance biosignatures for Earth-like planets has typically focused on analogues to spectral features produced by photosynthetic organisms on Earth, such as the vegetation red edge. Although oxygenic photosynthesis, facilitated by pigments evolved to capture photons, is the dominant metabolism on our planet, pigmentation has evolved for multiple purposes to adapt organisms to their environment. We present an interdisciplinary study of the diversity and detectability of nonphotosynthetic pigments as biosignatures, which includes a description of environments that host nonphotosynthetic biologically pigmented surfaces, and a lab-based experimental analysis of the spectral and broadband color diversity of pigmented organisms on Earth. We test the utility of broadband color to distinguish between Earth-like planets with significant coverage of nonphotosynthetic pigments and those with photosynthetic or nonbiological surfaces, using both 1-D and 3-D spectral models. We demonstrate that, given sufficient surface coverage, nonphotosynthetic pigments could significantly impact the disk-averaged spectrum of a planet. However, we find that due to the possible diversity of organisms and environments, and the confounding effects of the atmosphere and clouds, determination of substantial coverage by biologically produced pigments would be difficult with broadband colors alone and would likely require spectrally resolved data. Key Words: Biosignatures-Exoplanets-Halophiles-Pigmentation-Reflectance spectroscopy-Spectral models. Astrobiology 15, 341-361. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
27. Nonproteinogenic D-Amino Acids at Millimolar Concentrations Are a Toxin for Anaerobic Microorganisms Relevant to Early Earth and Other Anoxic Planets.
- Author
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Nixon, Sophie L. and Cockell, Charles S.
- Subjects
- *
ANAEROBIC microorganisms , *AMINO acids , *ANAEROBIC metabolism , *ASTROBIOLOGY , *GEOBACTER - Abstract
The delivery of extraterrestrial organics to early Earth provided a potentially important source of carbon and energy for microbial life. Optically active organic compounds of extraterrestrial origin exist in racemic form, yet life on Earth has almost exclusively selected for L- over D-enantiomers of amino acids. Although D-enantiomers of proteinogenic amino acids are known to inhibit aerobic microorganisms, the role of concentrated nonproteinogenic meteoritic D-amino acids on anaerobic metabolisms relevant to early Earth and other anoxic planets such as Mars is unknown. Here, we test the inhibitory effect of D-enantiomers of two nonproteinogenic amino acids common to carbonaceous chondrites, norvaline and α-aminobutyric acid, on microbial iron reduction. Three pure strains ( Geobacter bemidjiensis, Geobacter metallireducens, Geopsychrobacter electrodiphilus) and an iron-reducing enrichment culture were grown in the presence of 10 m M D-enantiomers of both amino acids. Further tests were conducted to assess the inhibitory effect of these D-amino acids at 1 and 0.1 m M. The presence of 10 m M D-norvaline and D- α-aminobutyric acid inhibited microbial iron reduction by all pure strains and the enrichment. G. bemidjiensis was not inhibited by either amino acid at 0.1 m M, but D- α-aminobutyric acid still inhibited at 1 m M. Calculations using published meteorite accumulation rates to the martian surface indicate D- α-aminobutyric acid may have reached inhibitory concentrations in little over 1000 years during peak infall. These data show that, on a young anoxic planet, the use of one enantiomer over another may render the nonbiological enantiomer an environmental toxin. Processes that generate racemic amino acids in the environment, such as meteoritic infall or impact synthesis, would have been toxic processes and could have been a selection pressure for the evolution of early racemases. Key Words: Microbial iron reduction-Amino acids-Toxicity. Astrobiology 15, 238-246. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
28. PELS (Planetary Environmental Liquid Simulator): A New Type of Simulation Facility to Study Extraterrestrial Aqueous Environments.
- Author
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Martin, Derek and Cockell, Charles S.
- Subjects
- *
PLANETARY atmospheres , *EXTRATERRESTRIAL beings , *GEOCHEMISTRY , *SPACE biology , *HABITABLE planets - Abstract
Investigations of other planetary bodies, including Mars and icy moons such as Enceladus and Europa, show that they may have hosted aqueous environments in the past and may do so even today. Therefore, a major challenge in astrobiology is to build facilities that will allow us to study the geochemistry and habitability of these extraterrestrial environments. Here, we describe a simulation facility (PELS: Planetary Environmental Liquid Simulator) with the capability for liquid input and output that allows for the study of such environments. The facility, containing six separate sample vessels, allows for statistical replication of samples. Control of pressure, gas composition, UV irradiation conditions, and temperature allows for the precise replication of aqueous conditions, including subzero brines under martian atmospheric conditions. A sample acquisition system allows for the collection of both liquid and solid samples from within the chamber without breaking the atmospheric conditions, enabling detailed studies of the geochemical evolution and habitability of past and present extraterrestrial environments. The facility we describe represents a new frontier in planetary simulation-continuous flow-through simulation of extraterrestrial aqueous environments. Key Words: Mars-Liquid-Saline-Planetary simulation. Astrobiology 15, 111-118. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
29. Trajectories of Martian Habitability.
- Author
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Cockell, Charles S.
- Subjects
- *
MARTIAN exploration , *MARTIAN atmosphere , *ARTIFICIAL atmospheres (Space environment) , *SPACE biology , *LIFE on Mars - Abstract
Beginning from two plausible starting points-an uninhabited or inhabited Mars-this paper discusses the possible trajectories of martian habitability over time. On an uninhabited Mars, the trajectories follow paths determined by the abundance of uninhabitable environments and uninhabited habitats. On an inhabited Mars, the addition of a third environment type, inhabited habitats, results in other trajectories, including ones where the planet remains inhabited today or others where planetary-scale life extinction occurs. By identifying different trajectories of habitability, corresponding hypotheses can be described that allow for the various trajectories to be disentangled and ultimately a determination of which trajectory Mars has taken and the changing relative abundance of its constituent environments. Key Words: Mars-Habitability-Liquid water-Planetary science. Astrobiology 14, 182-203. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
30. Limitations to a microbial iron cycle on Mars
- Author
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Nixon, Sophie L., Cockell, Charles S., and Tranter, Martyn
- Subjects
- *
IRON cycle (Biogeochemistry) , *ANAEROBIC microorganisms , *MICROBIAL metabolism , *OXIDATION-reduction reaction , *ELECTRON donor-acceptor complexes , *ORGANIC compounds , *MARS (Planet) - Abstract
Abstract: Anaerobic microbial metabolisms found on the Earth are the most plausible candidates for understanding potentially analogous energy gathering metabolisms on Mars. The iron-rich nature of Mars raises questions on whether the planet could support energy acquisition by iron-cycling microorganisms. This review paper addresses what is known about the redox couples that support microbial iron cycling on Earth, and evaluates evidence to date of the presence or absence of relevant redox constituents on Mars. We give particular focus to iron reduction. These constituents include the presence and prevalence of ferric iron-bearing minerals that may serve as terminal electron acceptors, and the likelihood of organic compounds (exogenous and endogenous) or hydrogen residing in the near- or sub-surface as a source of electron donors. Whilst it is feasible that redox couples for iron cycling may exist, or have existed in the past, current knowledge suggests that for chemolithotrophs (iron oxidation) Mars may be an electron acceptor limited world and that for chemoorganotrophs (iron reduction) Mars may be limited in widespread, readily available electron donors, particularly in its subsurface. There are several major limitations in this assessment due to lack of experimental data on Earth, and lack of measurements on Mars. We outline a series of high priority in-situ measurements that are necessary to fully evaluate the potential for a Martian biological iron cycle. Our conclusions also apply to the search for a Martian biological sulphur cycle. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
31. Limitations of microbial iron reduction under extreme conditions.
- Author
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Nixon, Sophie L, Bonsall, Emily, and Cockell, Charles S
- Subjects
- *
GIBBS' free energy , *IRON , *LIFE on Mars - Abstract
Microbial iron reduction is a widespread and ancient metabolism on Earth, and may plausibly support microbial life on Mars and beyond. Yet, the extreme limits of this metabolism are yet to be defined. To investigate this, we surveyed the recorded limits to microbial iron reduction in a wide range of characterized iron-reducing microorganisms (n = 141), with a focus on pH and temperature. We then calculated Gibbs free energy of common microbially mediated iron reduction reactions across the pH–temperature habitability space to identify thermodynamic limits. Comparing predicted and observed limits, we show that microbial iron reduction is generally reported at extremes of pH or temperature alone, but not when these extremes are combined (with the exception of a small number of acidophilic hyperthermophiles). These patterns leave thermodynamically favourable combinations of pH and temperature apparently unoccupied. The empty spaces could be explained by experimental bias, but they could also be explained by energetic and biochemical limits to iron reduction at combined extremes. Our data allow for a review of our current understanding of the limits to microbial iron reduction at extremes and provide a basis to test more general hypotheses about the extent to which biochemistry establishes the limits to life. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
32. Diverse microbial species survive high ammonia concentrations.
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Kelly, Laura C., Cockell, Charles S., and Summers, Stephen
- Subjects
- *
MICROORGANISMS , *AMMONIA , *PLANETARY theory , *INDUSTRIAL contamination , *SPACE microbiology , *ENVIRONMENTAL chemistry , *OXIDATION-reduction reaction , *SOIL sampling - Abstract
Planetary protection regulations are in place to control the contamination of planets and moons with terrestrial micro-organisms in order to avoid jeopardizing future scientific investigations relating to the search for life. One environmental chemical factor of relevance in extraterrestrial environments, specifically in the moons of the outer solar system, is ammonia (NH3). Ammonia is known to be highly toxic to micro-organisms and may disrupt proton motive force, interfere with cellular redox reactions or cause an increase of cell pH. To test the survival potential of terrestrial micro-organisms exposed to such cold, ammonia-rich environments, and to judge whether current planetary protection regulations are sufficient, soil samples were exposed to concentrations of NH3 from 5 to 35% (v/v) at −80°C and room temperature for periods up to 11 months. Following exposure to 35% NH3, diverse spore-forming taxa survived, including representatives of the Firmicutes (Bacillus, Sporosarcina, Viridibacillus, Paenibacillus, Staphylococcus and Brevibacillus) and Actinobacteria (Streptomyces). Non-spore forming organisms also survived, including Proteobacteria (Pseudomonas) and Actinobacteria (Arthrobacter) that are known to have environmentally resistant resting states. Clostridium spp. were isolated from the exposed soil under anaerobic culture. High NH3 was shown to cause a reduction in viability of spores over time, but spore morphology was not visibly altered. In addition to its implications for planetary protection, these data show that a large number of bacteria, potentially including spore-forming pathogens, but also environmentally resistant non-spore-formers, can survive high ammonia concentrations. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
33. Impact Disruption and Recovery of the Deep Subsurface Biosphere.
- Author
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Cockell, Charles S., Voytek, Mary A., Gronstal, Aaron L., Finster, Kai, Kirshtein, Julie D., Howard, Kieren, Reitner, Joachim, Gohn, Gregory S., Sanford, Ward E., Horton, J. Wright, Kallmeyer, Jens, Kelly, Laura, and Powars, David S.
- Subjects
- *
UNDERGROUND areas , *BIOSPHERE , *MICROBIOLOGY , *DISINTEGRATION of microorganisms , *BIOMASS , *GEOBIOLOGY - Abstract
Although a large fraction of the world's biomass resides in the subsurface, there has been no study of the effects of catastrophic disturbance on the deep biosphere and the rate of its subsequent recovery. We carried out an investigation of the microbiology of a 1.76 km drill core obtained from the ∼35 million-year-old Chesapeake Bay impact structure, USA, with robust contamination control. Microbial enumerations displayed a logarithmic downward decline, but the different gradient, when compared to previously studied sites, and the scatter of the data are consistent with a microbiota influenced by the geological disturbances caused by the impact. Microbial abundance is low in buried crater-fill, ocean-resurge, and avalanche deposits despite the presence of redox couples for growth. Coupled with the low hydraulic conductivity, the data suggest the microbial community has not yet recovered from the impact ∼35 million years ago. Microbial enumerations, molecular analysis of microbial enrichment cultures, and geochemical analysis showed recolonization of a deep region of impact-fractured rock that was heated to above the upper temperature limit for life at the time of impact. These results show how, by fracturing subsurface rocks, impacts can extend the depth of the biosphere. This phenomenon would have provided deep refugia for life on the more heavily bombarded early Earth, and it shows that the deeply fractured regions of impact craters are promising targets to study the past and present habitability of Mars. Key Words: Asteroid-Impacts-Subsurface biosphere-Subterranean environment-Geobiology. Astrobiology 12, 231-246. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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34. Uninhabited habitats on Mars
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Cockell, Charles S., Balme, Matt, Bridges, John C., Davila, Alfonso, and Schwenzer, Susanne P.
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- *
SPACE colonies , *BIOSPHERE , *MARTIAN meteorites , *GEOCHEMISTRY , *MARS (Planet) , *MARTIAN atmosphere , *EARTH (Planet) - Abstract
Abstract: Investigations of Mars as a potential location for life often make the assumption that where there are habitats, they will contain organisms. However, the observation of the ubiquitous distribution of life in habitable environments on the Earth does not imply the presence of life in martian habitats. Although uninhabited habitats are extremely rare on the Earth, a lack of a productive photosynthetic biosphere on Mars to generate organic carbon and oxygen, thus providing a rapidly available redox couple for energy acquisition by life and/or a lack of connectivity between habitats potentially increases the scope and abundance of uninhabited habitats for much of the geological history of the planet. Uninhabited habitats could have existed on Mars from the Noachian to the present-day in impact hydrothermal systems, megaflood systems, lacustrine environments, transient melted permafrost, gullies and local regions of volcanic activity; and there may be evidence for them in martian meteorites. Uninhabited habitats would provide control habitats to investigate the role of biology in planetary-scale geochemical processes on the Earth and they would provide new constraints on the habitability of Mars. Future robotic craft and samples returned from Mars will be able to directly show if uninhabited habitats exist or existed on Mars. [Copyright &y& Elsevier]
- Published
- 2012
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35. The Microbial Stages of Humanity.
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Cockell, Charles S
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HUMANITY , *MICROORGANISMS , *CIVILIZATION , *POLITICAL philosophy , *HISTORY - Abstract
The history of the development of human civilization mirrors the evolutionary innovations and habits of microorganisms. Escape from environmental extremes within caves (cryptoendolithic habitats) has given way to a predominantly surface-dwelling (epilithic) civilization. Humans, like microorganisms, extract minerals and elements from rocks - a form of biological rock weathering - which are fashioned into houses and other technology - a type of biomineralization. During the last century, humans have developed new microbial capabilities including travel from continent to continent in aircraft (spores) and the ability to produce toxins to kill other organisms. The biomineralizing, spore-forming, rock-inhabiting human biofilm will eventually expend its nutrients, unless, in a remarkable departure from the microbial world, humans on other planetary bodies return resources to their progenitor biofilm. Alternatively, as with microorganisms, the human biofilm will be forced to adapt to live in a nutrient-depleted world at much lower productivity or biomass than at present. Comparing humans with microbes, rather than other primates, yields a much more faithful interpretation of the development of our civilization and might provide new ways to model, mathematically and sociologically, the development of society. [ABSTRACT FROM AUTHOR] - Published
- 2011
- Full Text
- View/download PDF
36. Exposure of phototrophs to 548 days in low Earth orbit: microbial selection pressures in outer space and on early earth.
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Cockell, Charles S, Rettberg, Petra, Rabbow, Elke, and Olsson-Francis, Karen
- Subjects
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MICROBIAL selection , *BIOFILMS , *ULTRAVIOLET spectroscopy , *ANABAENA , *EARTH'S orbit , *EARTH (Planet) - Abstract
An epilithic microbial community was launched into low Earth orbit, and exposed to conditions in outer space for 548 days on the European Space Agency EXPOSE-E facility outside the International Space Station. The natural phototroph biofilm was augmented with akinetes of Anabaena cylindrica and vegetative cells of Nostoc commune and Chroococcidiopsis. In space-exposed dark controls, two algae (Chlorella and Rosenvingiella spp.), a cyanobacterium (Gloeocapsa sp.) and two bacteria associated with the natural community survived. Of the augmented organisms, cells of A. cylindrica and Chroococcidiopsis survived, but no cells of N. commune. Only cells of Chroococcidiopsis were cultured from samples exposed to the unattenuated extraterrestrial ultraviolet (UV) spectrum (>110 nm or 200 nm). Raman spectroscopy and bright-field microscopy showed that under these conditions the surface cells were bleached and their carotenoids were destroyed, although cell morphology was preserved. These experiments demonstrate that outer space can act as a selection pressure on the composition of microbial communities. The results obtained from samples exposed to >200 nm UV (simulating the putative worst-case UV exposure on the early Earth) demonstrate the potential for epilithic colonization of land masses during that time, but that UV radiation on anoxic planets can act as a strong selection pressure on surface-dwelling organisms. Finally, these experiments have yielded new phototrophic organisms of potential use in biomass and oxygen production in space exploration. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
37. Synthetic geomicrobiology: engineering microbe–mineral interactions for space exploration and settlement.
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Cockell, Charles S.
- Subjects
- *
GEOMICROBIOLOGY , *MICROBIAL genetic engineering , *REGOLITH , *SOIL formation , *SYNTHETIC biology , *SPACE exploration , *MARS (Planet) , *MOON , *OUTER space - Abstract
Synthetic geomicrobiology is a potentially new branch of synthetic biology that seeks to achieve improvements in microbe–mineral interactions for practical applications. In this paper, laboratory and field data are provided on three geomicrobiology challenges in space: (1) soil formation from extraterrestrial regolith by biological rock weathering and/or the use of regolith as life support system feedstock, (2) biological extraction of economically important elements from rocks (biomining) and (3) biological solidification of surfaces and dust control on other planetary surfaces. The use of synthetic or engineered organisms in these three applications is discussed. These three examples are used to extract general common principles that might be applied to the design of organisms used in synthetic geomicrobiology. [ABSTRACT FROM PUBLISHER]
- Published
- 2011
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38. Vacant habitats in the Universe
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Cockell, Charles S.
- Subjects
- *
EXTRATERRESTRIAL life , *HABITATS , *VACANT lands , *FATS & oils , *HABITABLE planets , *GEOCHEMISTRY , *STERILIZATION (Disinfection) , *IMPACT craters ,UNIVERSE - Abstract
The search for life on other planets usually makes the assumption that where there is a habitat, it will contain life. On the present-day Earth, uninhabited habitats (or vacant habitats) are rare, but might occur, for example, in subsurface oils or impact craters that have been thermally sterilized in the past. Beyond Earth, vacant habitats might similarly exist on inhabited planets or on uninhabited planets, for example on a habitable planet where life never originated. The hypothesis that vacant habitats are abundant in the Universe is testable by studying other planets. In this review, I discuss how the study of vacant habitats might ultimately inform an understanding of how life has influenced geochemical conditions on Earth. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
39. Astrobiology-What Can We Do on the Moon?
- Author
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Cockell, Charles S.
- Subjects
- *
SPACE biology , *LUNAR exploration , *MARTIAN exploration , *BIOLOGISTS , *LIFE sciences - Abstract
The Moon does not seem to be a place for a biologist. However, it offers the possibility of unravelling a better understanding of the conditions for habitability on the Earth and the conditions for life on the early Earth. It will be a place where much of the life sciences technologies required to establish a permanent human presence in space can be tested to complete reliability. Specifically, a long-term life sciences laboratory on the Moon can be used to investigate three areas of science that are currently poorly understood: (1) the linearity or non-linearity of the effects of different magnitudes of space environmental stresses on organisms, particularly gravity; (2) the effects of cumulative environmental effects both in individual organisms and across generations, (3) the synergistic effects of different space environmental parameters on organisms. The close proximity and scientific importance of the Moon makes it a useful permanent location and staging post for the human expansion into space. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
40. Bacterial Diversity of Weathered Terrestrial Icelandic Volcanic Glasses.
- Author
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Kelly, Laura C., Cockell, Charles S., Piceno, Yvette M., Andersen, Gary L., Thorsteinsson, Thorsteinn, and Marteinsson, Viggo
- Subjects
- *
BACTERIA , *MINERALOGY , *ACTINOBACTERIA , *GENES , *DATABASES - Abstract
The diversity of microbial communities inhabiting two terrestrial volcanic glasses of contrasting mineralogy and age was characterised. Basaltic glass from a <0.8 Ma hyaloclastite deposit (Valafell) harboured a more diverse Bacteria community than the younger rhyolitic glass from ∼150-300 AD (Dόmadalshraun lava flow). Actinobacteria dominated 16S rRNA gene clone libraries from both sites, however, Proteobacteria, Acidobacteria and Cyanobacteria were also numerically abundant in each. A significant proportion (15-34%) of the sequenced clones displayed <85% sequence similarities with current database sequences, thus suggesting the presence of novel microbial diversity in each volcanic glass. The majority of clone sequences shared the greatest similarity to uncultured organisms, mainly from soil environments, among these clones from Antarctic environments and Hawaiian and Andean volcanic deposits. Additionally, a large number of clones within the Cyanobacteria and Proteobacteria were more similar to sequences from other lithic environments, included among these Icelandic clones from crystalline basalt and rhyolite, however, no similarities to sequences reported from marine volcanic glasses were observed. PhyloChip analysis detected substantially greater numbers of phylotypes at both sites than the corresponding clone libraries, but nonetheless also identified the basaltic glass community as the richer, containing approximately 29% unique phylotypes compared to rhyolitic glass. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
41. Use of cyanobacteria for in-situ resource use in space applications
- Author
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Olsson-Francis, Karen and Cockell, Charles S.
- Subjects
- *
CYANOBACTERIA , *SPACE microbiology , *REGOLITH , *WEATHERING , *MARS (Planet) , *MOON - Abstract
Abstract: The regolith of other planetary bodies, such as the Moon and Mars, is rich in inorganic elements that could potentially be exploited for space applications. Lithotrophic microorganisms that are capable of utilising rocks as a growth substrate, and facilitate the extraction of elements, are ideal candidates for in-situ resource use. Of particular interest are the cyanobacteria, which have been suggested for applications, such as oxygen, fuel and biomass production, nutrient acquisition, and feedstock provisions. In this study, Gloeocapsa strain OU_20, isolated from a rock-dwelling community exposed to low Earth orbit; Leptolyngbya strain OU_13 and Phormidium strain OU_10, both isolated from a rock-dwelling community exposed to Mars simulated conditions; Chroococcidiopsis 029; Arthrospira platensis; Synechococcus elongatus; and Anabaena cylindrica, were examined as potential organisms for space in-situ resource use. Volcanic rocks, including basalt (low in SiO2) analogous to martian and lunar basalt, rhyolite (high in SiO2), and anorthosite analogous to lunar regolith were used as growth substrates. The growth rate and rock dissolution were significantly lower with rhyolite demonstrating the importance of silica content in defining the potential for in-situ resource use. Biological weathering resulted in the release of bio-essential elements from the rock matrix, highlighting the potential of cyanobacteria for applications such as bio-mining and nutrient acquisition, on other planets. A. cylindrica produced the maximum biomass with the three rock-types and the optimal value was obtained with the basalt. Exposure experiments demonstrated that A. cylindrica, Chroococcidiopsis 029, Gloeocapsa strain OU_20, Phormidium strain OU_10, and Leptolyngbya strain OU_13 were able to survive 28 days of exposure to desiccation and Mars simulated conditions, which is beneficial in case of system malfunction and for storage. The results from this study indicate that cyanobacteria can potentially be used for in-situ planetary resource acquisition. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
42. Geomicrobiology beyond Earth: microbe–mineral interactions in space exploration and settlement
- Author
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Cockell, Charles S.
- Subjects
- *
SPACE microbiology , *EXTRATERRESTRIAL microorganisms , *BIOMARKERS , *MANUFACTURING processes , *LIFE support systems (Space environment) , *GEOMICROBIOLOGY , *SOIL microbiology , *SPACE exploration , *OUTER space , *EARTH (Planet) - Abstract
Geomicrobiology investigates the interactions of microorganisms with geological substrates, and this branch of microbiology has enormous potential in the exploration and settlement of space. Microorganisms can be used to extract useful elements from extraterrestrial materials for industrial processes or for use as nutrients in life support systems. In addition, microorganisms could be used to create soil from lunar and Martian rocks. Furthermore, understanding the interactions of microorganisms with rocks is essential for identifying mineral biomarkers to be used in the search for life on other planetary bodies. Increasing space exploration activities make geomicrobiology an important applied science beyond Earth. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
43. Experimental methods for studying microbial survival in extraterrestrial environments
- Author
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Olsson-Francis, Karen and Cockell, Charles S.
- Subjects
- *
SPACE microbiology , *SPACE environment , *SIMULATION methods & models , *BIOLOGICAL models , *MICROBIOLOGY experiments , *MICROBIAL cultures , *BIOTIC communities - Abstract
Abstract: Microorganisms can be used as model systems for studying biological responses to extraterrestrial conditions; however, the methods for studying their response are extremely challenging. Since the first high altitude microbiological experiment in 1935 a large number of facilities have been developed for short- and long-term microbial exposure experiments. Examples are the BIOPAN facility, used for short-term exposure, and the EXPOSE facility aboard the International Space Station, used for long-term exposure. Furthermore, simulation facilities have been developed to conduct microbiological experiments in the laboratory environment. A large number of microorganisms have been used for exposure experiments; these include pure cultures and microbial communities. Analyses of these experiments have involved both culture-dependent and independent methods. This review highlights and discusses the facilities available for microbiology experiments, both in space and in simulation environments. A description of the microorganisms and the techniques used to analyse survival is included. Finally we discuss the implications of microbiological studies for future missions and for space applications. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
44. Advancing the case for microbial conservation.
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Cockell, Charles S. and Jones, Harriet L.
- Subjects
- *
BACTERIA , *BIODIVERSITY , *BIOSPHERE , *CORALS , *MICROORGANISMS - Abstract
The majority of the biomass and biodiversity of life on the Earth is accounted for by microbes. They play pivotal roles in biogeochemical cycles and harbour novel metabolites that have industrial uses. For these reasons the conservation of microbial ecosystems, communities and even specific taxa should be a high priority. We review the reasons for including microorganisms in conservation agenda. We discuss some of the complications in this endeavour, including the unresolved argument about whether microorganisms have intrinsic value, which influences some of the non instrumental motivations for their conservation and, from a more pragmatic perspective, exactly what it is that we seek to conserve (microorganisms, their habitats or their gene pools). Despite complications, priorities can be defined for microbial conservation and we provide practical examples of such priorities. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
45. Planetary targets in the search for extrasolar oxygenic photosynthesis.
- Author
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Cockell, Charles S., Raven, John A., Kaltenegger, Lisa, and Logan, Roberta C.
- Subjects
- *
SPACE telescopes , *PHOTOSYNTHESIS , *PHOTOSYNTHETICALLY active radiation (PAR) , *EARTH (Planet) , *EQUILIBRIUM , *OXYGEN - Abstract
Background: In the coming decades space telescopes will be constructed that will attempt to find the gaseous products of oxygenic photosynthesis, the most promising biosignatures of life, in the atmospheres of temperate Earth-like planets orbiting distant stars. Aims: This paper aims to provide a synthesis of the range of feasible targets - either planets or their satellites - that could harbour photosynthesis. Methods: We calculated photosynthetically active radiation (PAR) fluxes on a diversity of planetary bodies including those receiving direct light from a single star, similarly to the Earth, and investigated the potential of these fluxes to support photosynthesis. Results: All main sequence stars emit radiation that is capable of supporting photosynthesis on Earth-like planets. We discuss tidally-locked M star planets as a special case. Less conventional targets for searches include large moons orbiting gas giant planets, which receive reflected light from their host planets and from the host star, planets in stable orbits in binary star systems, and the search for two planets within the same star system with photosynthetic signatures. Conclusions: A diversity of planetary bodies are targets in the search for extrasolar photosynthesis. The demonstration that many or none of these candidate planetary bodies harbour photosynthesis would be an important conclusion in understanding the evolution and prevalence of photosynthesis. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
46. Darwin—an experimental astronomy mission to search for extrasolar planets.
- Author
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Cockell, Charles S., Herbst, Tom, Léger, Alain, Absil, O., Beichman, Charles, Benz, Willy, Brack, Andre, Chazelas, Bruno, Chelli, Alain, Cottin, Hervé, Coudé du Foresto, Vincent, Danchi, William, Defrère, Denis, Herder, Jan-Willem, Eiroa, Carlos, Fridlund, Malcolm, Henning, Thomas, Johnston, Kenneth, Kaltenegger, Lisa, and Labadie, Lucas
- Subjects
- *
DETECTION of extrasolar planets , *INTERFEROMETERS , *IMAGING systems in astronomy , *EARTH (Planet) , *ASTRONOMICAL spectroscopy , *ASTRONOMY - Abstract
As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
47. Alteration textures in terrestrial volcanic glass and the associated bacterial community.
- Author
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Cockell, Charles S., Olsson-Francis, K., Herrera, A., and Meunier, A.
- Subjects
- *
GLASS , *BASALT , *OBSIDIAN , *RHYOLITE , *MINERALOGICAL research - Abstract
Alteration textures were examined in subglacial (hyaloclastite) deposits at Valafell, Southern Iceland. Pitted and ‘elongate’ alteration features are observed in the glass similar to granular and tubular features reported previously in deep-ocean basaltic glasses, but elongate features generally did not have a length to width ratio greater than five. Elongate features were found in only 7% of surfaces. Crystalline basalt clasts, which are incorporated into the hyaloclastite, did not display elongate structures. Pitted alteration features were poorly defined in crystalline basalt, comprising only 4% of the surface compared to 47% in the case of basaltic glass. Examination of silica-rich glass (obsidian) and rhyolite similarly showed poorly defined pitted textures that comprised less than 15% of the surface and no elongate features were observed. These data highlight the differences in alteration textures between terrestrial basaltic glass and previously studied deep-ocean and subsurface basaltic glass, and the important role of mineralogy in controlling the type and abundance of alteration features. The hyaloclastite contains a diverse and abundant bacterial population, as determined by 16S rDNA analysis, which could be involved in weathering the glass. Despite the presence of phototrophs, we show that they were not involved in the production of most alteration textures in the basaltic glass materials we examined. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
48. Interstellar planetary protection
- Author
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Cockell, Charles S.
- Subjects
- *
DETECTION of extrasolar planets , *SPACE vehicles , *SPACE exploration , *ASTRONAUTICS , *SPACE environment , *ASTROPHYSICS , *OUTER space - Abstract
Abstract: In the coming decades the detection of Earth-like extrasolar planets, either apparently lifeless or exhibiting spectral signatures of life, will encourage design studies for craft to visit them. These missions will require the elaboration of an interstellar planetary protection protocol. Given a specific dose required to sterilize microorganisms on a spacecraft, a critical mean velocity can be determined below which a craft becomes self-sterilizing. This velocity is calculated to be below velocities previously projected for interstellar missions, suggesting that an active sterilization protocol prior to launch might be required. Given uncertainties in the surface conditions of a destination extrasolar planet, particularly at microscopic scales, the potential for unknown biochemistries and biologies elsewhere, or the possible inoculation of a lifeless planet that is habitable, then both lander and orbiter interstellar missions should be completely free of all viable organisms, necessitating a planetary protection approach applied to orbiters and landers bound for star systems with unknown local conditions for habitability. I discuss the case of existing craft on interstellar trajectories – Pioneer 10, 11 and Voyager 1 and 2. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
49. ENVIRONMENTAL ETHICS AND SIZE.
- Author
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Cockell, Charles S.
- Subjects
- *
ENVIRONMENTAL policy , *ENVIRONMENTAL ethics , *THOUGHT experiments , *ENVIRONMENTALISM , *ENVIRONMENTAL law , *CONTINGENT valuation , *BODY size - Abstract
Environmental policy has a size bias. Small organisms, such as microorganisms, command less attention from environmentalists than larger organisms, such as birds and large mammals. A simple thought experiment involving microscopic polar bears and giant microorganisms illustrates the importance of size in environmental ethics. Given the positive correlation between body size and brain size, there is probably a basis for a size bias in environmental ethics using ethical frameworks based on conations. This paper examines the relevance of the size of organisms in environmental ethics. It emphasizes the need to understand the theoretical reasons for the importance of size, and not to base a size bias merely on a subjective anthropocentric prejudice favouring large organisms. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
50. Why are some microorganisms boring?
- Author
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Cockell, Charles S. and Herrera, Aude
- Subjects
- *
MICROORGANISMS , *WEATHERING , *ROCKS , *CARBONATES , *BIOLOGICAL evolution , *ULTRAVIOLET radiation - Abstract
Microorganisms from diverse environments actively bore into rocks, contributing significantly to rock weathering. Carbonates are the most common substrate into which they bore, although there are also reports of microbial borings into volcanic glass. One of the most intriguing questions in microbial evolutionary biology is why some microorganisms bore. A variety of possible selection pressures, including nutrient acquisition, protection from UV radiation and predatory grazing could promote boring. None of these pressures is mutually exclusive and many of them could have acted in concert with varying strengths in different environments to favour the development of microorganisms that bore. We suggest that microbial boring might have begun in some environments as a mechanism against entombment by mineralization. [Copyright &y& Elsevier]
- Published
- 2008
- Full Text
- View/download PDF
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