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The 2-week, virtual Future of the Search for Life science and engineering workshop brought together more than 100 scientists, engineers, and technologists in March and April 2022 to provide their expert opinion on the interconnections between life-detection science and technology. Participants identified the advances in measurement and sampling technologies they believed to be necessary to perform in situ searches for life elsewhere in our Solar System, 20 years or more in the future. Among suggested measurements for these searches, those pertaining to three potential indicators of life termed "dynamic disequilibrium," "catalysis," and "informational polymers" were identified as particularly promising avenues for further exploration. For these three indicators, small breakout groups of participants identified measurement needs and knowledge gaps, along with corresponding constraints on sample handling (acquisition and processing) approaches for a variety of environments on Enceladus, Europa, Mars, and Titan. Despite the diversity of these environments, sample processing approaches all tend to be more complex than those that have been implemented on missions or envisioned for mission concepts to date. The approaches considered by workshop breakout groups progress from nondestructive to destructive measurement techniques, and most involve the need for fluid (especially liquid) sample processing. Sample processing needs were identified as technology gaps. These gaps include technology and associated sampling strategies that allow the preservation of the thermal, mechanical, and chemical integrity of the samples upon acquisition; and to optimize the sample information obtained by operating suites of instruments on common samples. Crucially, the interplay between science-driven life-detection strategies and their technological implementation highlights the need for an unprecedented level of payload integration and extensive collaboration between scientists and engineers, starting from concept formulation through mission deployment of life-detection instruments and sample processing systems. [ABSTRACT FROM AUTHOR]

As of mid-2023 at least ten missions are in development or being planned to explore Venus in the next 2 decades. Most of these emphasize atmospheric chemistry and surface/interior scientific objectives and only a few directly address past and present habitability of Venus as a primary science goal. All of the missions employ previously flight-tested platforms—Orbiters and general atmospheric probes, yet none (as of yet) plan to utilize longer-lived atmospheric platforms (e.g., balloons or airships) or landers. Thus several key questions about Venus will necessarily remain unanswered after the current wave of missions in development which will explore Venus starting in 2029 and continuing throughout the 2030s. This future-oriented perspective outlines the major scientific questions that the next-generation of missions to Venus should address for a better understanding of the planet as a system and provide a reliable comparative basis for the Venus-analogue exoplanets which can be investigated only by means of remote observations such as from the James Webb Space Telescope (JWST). This next generation of Venus missions may require long lived atmospheric platforms that either float or which “fly” at different altitudes, longer lived surface stations, and eventually samples of the atmosphere/cloud particles (aerosols) and surface returned to Earth laboratories. Although ideas for aerial platforms, long-lived landers, and missions to return atmospheric and surface samples are being conceptualized at present to be ready for upcoming international competed opportunities (e.g., NASA, ESA, ISRO, JAXA), they await further investment in technologies to provide the combination of scientific measurement capabilities and flight-system performance to make the breakthroughs that the community will expect, guided by longstanding science priorities.

The search for life elsewhere in the universe is one of the central aims of science in the twent-first century. While most of this work is aimed at planets orbiting other stars, the search for life in our own Solar System is an important part of this endeavour. Venus is often thought to have too harsh an environment for life, but it may have been a more hospitable place in the distant past. If life evolved there in the past then the cloud decks of Venus are the only remaining niche where life as we know it might survive today. The discovery of the molecule phosphine, PH 3 , in these clouds has reinvigorated research looking into the possibility of life in the clouds. In this review we examine the background to studies of the possibility of life on Venus, discuss the discovery of phosphine, review conflicting and confirming observations and analyses, and then look forward to future observations and space missions that will hopefully provide definitive answers as to the origin of phosphine on Venus and to the question of whether life might exist there. [ABSTRACT FROM AUTHOR]

The identification of reliable biomarkers, such as amino acids, is key for the search of extraterrestrial life. A large number of microorganisms metabolize, synthesize, take up and excrete amino acids as part of the amino acid metabolism during aerobic and/or anaerobic respiration or in fermentation. In this work, we investigated whether the anaerobic microbial metabolism of amino acids could leave a secondary biosignature indicating biological activity in the environment around the cells. The observed fingerprints would reflect the physiological capabilities of the specific microbial community under investigation. The metabolic processing of an amino acid mixture by two distinct anaerobic microbial communities collected from Islinger Mühlbach (ISM) and Sippenauer Moor (SM), Germany was examined. The amino acid mixture contained L-alanine, β-alanine, L-aspartic acid, DL-proline, L-leucine, L-valine, glycine, L-phenylalanine and L-isoleucine. In parallel, an amino acid spiked medium without microorganisms was used as a control to determine abiotic changes over time. Liquid chromatography mass spectrometry (LC-MS) was used to track amino acid changes over time. When comparing to the control samples that did not show significant changes of amino acids concentrations over time, we found that glycine was almost completely depleted from both microbial samples to less than 3% after the first two weeks- This results indicates a preferential use of this simple amino acid by these microbial communities. Although glycine degradation can be caused by abiotic processes, these results show that its preferential depletion in an environment would be consistent with the presence of life. We found changes in most other amino acids that varied between amino acids and communities, suggesting complex dynamics with no clear universal pattern that might be used as a signature of life. However, marked increases in amino acids, caused by cellular synthesis and release into the extracellular environment (e.g., alanine), were observed and could be considered a signature of metabolic activity. We conclude, that substantial anomalous enhancements of some amino acids against the expected abiotic background concentration may be an agnostic signature of the presence of biological processes.

We have developed a compact instrument called the "COmpact COlor BIofinder", or CoCoBi, for the standoff detection of biological materials and organics with polyaromatic hydrocarbons (PAHs) using a nondestructive approach in a wide area. The CoCoBi system uses a compact solid state, conductively cooled neodymium-doped yttrium aluminum garnet (Nd:YAG) nanosecond pulsed laser capable of simultaneously providing two excitation wavelengths, 355 and 532 nm, and a compact, sensitive-gated color complementary metal–oxide–semiconductor camera detector. The system is compact, portable, and determines the location of biological materials and organics with PAHs in an area 1590 cm2 wide, from a target distance of 3 m through live video using fast fluorescence signals. The CoCoBi system is highly sensitive and capable of detecting a PAH concentration below 1 part per billion from a distance of 1 m. The color images provide the simultaneous detection of various objects in the target area using shades of color and morphological features. We demonstrate that this unique feature successfully detected the biological remains present in a 150-million-year-old fossil buried in a fluorescent clay matrix. The CoCoBi was also successfully field-tested in Hawaiian ocean water during daylight hours for the detection of natural biological materials present in the ocean. The wide-area and video-speed imaging capabilities of CoCoBi for biodetection may be highly useful in future NASA rover–lander life detection missions. Graphical Abstract [ABSTRACT FROM AUTHOR]

Perseverance is on Mars, collecting samples which will inform about Martian geology and paleoenvironmental conditions. However, the surface of Mars is continuously bombarded by ionizing and non-ionizing radiation, including UVs, which may significantly alter hydrated mineral phases such as sulfates, phosphates and carbonates. To explore and constrain this effect, we experimentally exposed pellets of more or less hydrated minerals to UV radiation within a Martian chamber at a temperature relevant for the rocks at the surface of Mars. Results show that exposure to UV leads to a strong alteration of the Raman and IR signals of sulfates, phosphates and carbonates. The strong increase of the luminescence signals coupled to the decrease of the Raman signals relatively to the background and the clear attenuation of the IR signals are interpreted as caused by an increasing concentration of electronic defects. The present results have major implications for the ongoing exploration of Mars: one should not expect to detect pristine materials, except over freshly excavated surfaces. Still, as a precaution, all the targets measured or collected on Mars should be considered as having been exposed to UV radiation to some extent. • The surface of Mars is continuously bombarded by ionizing and non-ionizing radiation. • Here we experimentally investigate the effect of UVs on spectral signals of minerals. • Exposure to UVs alters Raman and IR signals of sulfates, phosphates and carbonates. • Exposure to UVs clearly enhances the creation of electronic defects. • Such effect has to be taken into account when interpreting data collected on Mars. [ABSTRACT FROM AUTHOR]

Here we review published studies on the abundance and diversity of terrestrial rock-hosted life, the environments it inhabits, the evolution of its metabolisms, and its fossil biomarkers to provide guidance in the search for life on Mars. Key findings are (1) much terrestrial deep subsurface metabolic activity relies on abiotic energy-yielding fluxes and in situ abiotic and biotic recycling of metabolic waste products rather than on buried organic products of photosynthesis; (2) subsurface microbial cell concentrations are highest at interfaces with pronounced chemical redox gradients or permeability variations and do not correlate with bulk host rock organic carbon; (3) metabolic pathways for chemolithoautotrophic microorganisms evolved earlier in Earth's history than those of surface-dwelling phototrophic microorganisms; (4) the emergence of the former occurred at a time when Mars was habitable, whereas the emergence of the latter occurred at a time when the martian surface was not continually habitable; (5) the terrestrial rock record has biomarkers of subsurface life at least back hundreds of millions of years and likely to 3.45 Ga with several examples of excellent preservation in rock types that are quite different from those preserving the photosphere-supported biosphere. These findings suggest that rock-hosted life would have been more likely to emerge and be preserved in a martian context. Consequently, we outline a Mars exploration strategy that targets subsurface life and scales spatially, focusing initially on identifying rocks with evidence for groundwater flow and low-temperature mineralization, then identifying redox and permeability interfaces preserved within rock outcrops, and finally focusing on finding minerals associated with redox reactions and associated traces of carbon and diagnostic chemical and isotopic biosignatures. Using this strategy on Earth yields ancient rock-hosted life, preserved in the fossil record and confirmable via a suite of morphologic, organic, mineralogical, and isotopic fingerprints at micrometer scale. We expect an emphasis on rock-hosted life and this scale-dependent strategy to be crucial in the search for life on Mars. [ABSTRACT FROM AUTHOR]

Prokaryotic life has dominated most of the evolutionary history of our planet, evolving to occupy virtually all available environmental niches. Extremophiles, especially those thriving under multiple extremes, represent a key area of research for multiple disciplines, spanning from the study of adaptations to harsh conditions, to the biogeochemical cycling of elements. Extremophile research also has implications for origin of life studies and the search for life on other planetary and celestial bodies. In this article, we will review the current state of knowledge for the biospace in which life operates on Earth and will discuss it in a planetary context, highlighting knowledge gaps and areas of opportunity.

With advances in commercial space launch capabilities and reduced costs to orbit, humans may arrive on Mars within a decade. Both to preserve any signs of past (and extant) martian life and to protect the health of human crews (and Earth's biosphere), it will be necessary to assess the risk of cross-contamination on the surface, in blown dust, and into the near-subsurface (where exploration and resource-harvesting can be reasonably anticipated). Thus, evaluating for the presence of life and biosignatures may become a critical-path Mars exploration precursor in the not-so-far future, circa 2030. This Special Collection of papers from the Atacama Rover Astrobiology Drilling Studies (ARADS) project describes many of the scientific, technological, and operational issues associated with searching for and identifying biosignatures in an extreme hyperarid region in Chile's Atacama Desert, a well-studied terrestrial Mars analog environment. This paper provides an overview of the ARADS project and discusses in context the five other papers in the ARADS Special Collection, as well as prior ARADS project results.

Prokaryotic life has dominated most of the evolutionary history of our planet, evolving to occupy virtually all available environmental niches. Extremophiles, especially those thriving under multiple extremes, represent a key area of research for multiple disciplines, spanning from the study of adaptations to harsh conditions, to the biogeochemical cycling of elements. Extremophile research also has implications for origin of life studies and the search for life on other planetary and celestial bodies. In this article, we will review the current state of knowledge for the biospace in which life operates on Earth and will discuss it in a planetary context, highlighting knowledge gaps and areas of opportunity. [ABSTRACT FROM AUTHOR]

In this study, we attempt to illustrate the competition that constitutes the main challenge of astrobiology, namely the competition between the probability of extraterrestrial life and its detectability. To illustrate this fact, we propose a simple statistical approach based on our knowledge of the Universe and the MilkyWay, the Solar System, and the evolution of life on Earth permitting us to obtain the order of magnitude of the distance between Earth and bodies inhabited by more or less evolved past or present life forms, and the consequences of this probability for the detection of associated biosignatures. We thus show that the probability of the existence of evolved extraterrestrial forms of life increases with distance from the Earth while, at the same time, the number of detectable biosignatures decreases due to technical and physical limitations. This approach allows us to easily explain to the general public why it is very improbable to detect a signal of extraterrestrial intelligence while it is justified to launch space probes dedicated to the search for microbial life in the Solar System. [ABSTRACT FROM AUTHOR]

The detection of exoplanets orbiting other stars has revolutionized our view of the cosmos. First results suggest that it is teeming with a fascinating diversity of rocky planets, including those in the habitable zone. Even our closest star, Proxima Centauri, harbors a small planet in its habitable zone, Proxima b. With the next generation of telescopes, we will be able to peer into the atmospheres of rocky planets and get a glimpse into other worlds. Using our own planet and its wide range of biota as a Rosetta stone, we explore how we could detect habitability and signs of life on exoplanets over interstellar distances. Current telescopes are not yet powerful enough to characterize habitable exoplanets, but the next generation of telescopes that is already being built will have the capabilities to characterize close-by habitable worlds. The discussion on what makes a planet a habitat and how to detect signs of life is lively. This review will show the latest results, the challenges of how to identify and characterize such habitable worlds, and how near-future telescopes will revolutionize the field. For the first time in human history, we have developed the technology to detect potential habitable worlds. Finding thousands of exoplanets has taken the field of comparative planetology beyond the Solar System. [ABSTRACT FROM AUTHOR]

The second ExoMars mission will be launched in 2020 to target an ancient location interpreted to have strong potential for past habitability and for preserving physical and chemical biosignatures (as well as abiotic/prebiotic organics). The mission will deliver a lander with instruments for atmospheric and geophysical investigations and a rover tasked with searching for signs of extinct life. The ExoMars rover will be equipped with a drill to collect material from outcrops and at depth down to 2 m. This subsurface sampling capability will provide the best chance yet to gain access to chemical biosignatures. Using the powerful Pasteur payload instruments, the ExoMars science team will conduct a holistic search for traces of life and seek corroborating geological context information. [ABSTRACT FROM AUTHOR]

In this study, we attempt to illustrate the competition that constitutes the main challenge of astrobiology, namely the competition between the probability of extraterrestrial life and its detectability. To illustrate this fact, we propose a simple statistical approach based on our knowledge of the Universe and the Milky Way, the Solar System, and the evolution of life on Earth permitting us to obtain the order of magnitude of the distance between Earth and bodies inhabited by more or less evolved past or present life forms, and the consequences of this probability for the detection of associated biosignatures. We thus show that the probability of the existence of evolved extraterrestrial forms of life increases with distance from the Earth while, at the same time, the number of detectable biosignatures decreases due to technical and physical limitations. This approach allows us to easily explain to the general public why it is very improbable to detect a signal of extraterrestrial intelligence while it is justified to launch space probes dedicated to the search for microbial life in the Solar System.

Abstract: The paper by Perry et al. (2007, Defining biominerals and organominerals: Direct and indirect indicators of life, Sedimentary Geology, 201, 157–179) proposes to introduce “the new term ‘organomineral’” to describe mineral products whose formation is induced by by-products of biological activity, dead and decaying organisms, or nonbiological organic compounds, to be distinguished from the biomineral components of living organisms. The substantive ‘organomineral’, however, is not new: it was first introduced in 1993, with basically the same definition and distinction from biominerals, at the 7th International Symposium on Biomineralization (Défarge and Trichet, 1995, From biominerals to ‘organominerals’: The example of the modern lacustrine calcareous stromatolites from Polynesian atolls, Bulletin de l''Institut Océanographique de Monaco, n° spéc. 14, vol. 2, pp. 265–271). Thereafter, more than twenty-five papers by various authors have been devoted to organominerals and organomineral formation (‘organomineralization’) processes. Only two of these papers are cited by Perry et al., and without any reference to the definitions, or even the terms ‘organomineral’ or ‘organomineralization’, which they included. Moreover, Perry et al. tend to enlarge the original concept of organomineral to encompass all minerals containing organic matter, whether these organic compounds are active or passive in the mineralization, which introduces ambiguities detrimental to a fine understanding of present and past geobiological processes. Finally, Perry et al. propose to consider organominerals as indirect biosignatures that could be used in the search for evidence of life in the geological record and extraterrestrial bodies. This latter proposition also is problematical, in that organominerals may be formed in association with prebiotic or abiotic organic matter. [Copyright &y& Elsevier]

There is at present a possibility for returning to Europa with LAPLACE, a mission to Europa and the Jupiter System for European Space Agency's Cosmic Vision Programme. The question of habitability by the identification of reliable bio-indicators is a major priority. We explain the options for approaching the question of selecting the right instrumentation for measuring the more abundant sulphur isotope, in spite of the fact that 32S is isobaric (same m/z) with 16O2. Two technologies are available for investigating the possible biogenicity of the surficial sulphur on the icy patches discovered by the Galileo mission. We argue that there is a need to use higher-order statistics in the data that are to be gathered with the instruments chosen for the payload (ion-traps for orbital measurements, or penetrators for surficial measurements). In particular, we argue in favour of data analysis taken from an orbital spacecraft that addresses fluctuations of the data retrieved, rather than the mean. For this purpose, we reconsider the significance of deviations of sulphur abundances relative to normal (meteoritic) values. In the present work, we consider the experimentally testable possibility of biogenically driven isotopic anomalies in the light of statistical data analysis. The fluctuation test that is being proposed in the context of future missions to Europa may well be appropriate to a laboratory experiment with sulphur-reducing bacteria with the corresponding isotopic fractionation. [ABSTRACT FROM AUTHOR]

Abstract: Autonomy will play a key role in future science-driven, tier-scalable robotic planetary reconnaissance to extremely challenging (by existing means), locales on Mars and elsewhere that have the potential to yield significant geological and possibly exobiologic information. The full-scale and optimal deployment of the agents employed by tier-scalable architectures requires the design, implementation, and integration of an intelligent reconnaissance system. Such a system should be designed to enable fully automated and comprehensive characterization of an operational area, as well as to integrate existing information with acquired, “in transit” spatial and temporal sensor data, to identify and home in on prime candidate locales. These may include locales with the greatest potential of containing life. Founded on the premise that water and energy are key to life, we have designed a fuzzy system that can (1) acquire the appropriate past/present water/energy indicators while the tier-scalable mission architecture is deployed (first layer), and (2) evaluate habitability through a specialized fuzzy knowledge-base of the water and energy information (second layer) acquired in (1). The system has been tested through hypothetical deployments at two hypothesized regions on Mars. The fuzzy-based expert''s simulation results corroborate the same conclusions provided by the human expert, and thus highlight the system''s potential capability to effectively and autonomously reason as an interdisciplinary scientist in the quest for life. While the approach is demonstrated for Mars, the methodology is general enough to be extended to other planetary bodies. It can be readily modified and updated as our interdisciplinary understanding of planetary environments improves. We believe this work represents a foundational step toward implementing higher-level intelligence in robotic, tier-scalable planetary reconnaissance within and beyond the solar system. [Copyright &y& Elsevier]

Abstract: If life ever existed on Mars, a key question is the genetic relationship of that life to life on Earth. To determine if Martian life represents a separate, second genesis of life requires the analysis of organisms, not fossils. Ancient permafrost on Mars represents one potential source of intact, albeit probably dead by radiation, Martian organisms. Strong crustal magnetism in the ancient heavily cratered southern highlands between 60 and 80°S and at about 180°W indicates what may be the oldest, best preserved ice-rich permafrost on Mars. Drilling to depths of 1000m would reach samples unaffected by possible warming due to cyclic changes in Mars’ obliquity. When drilling into the permafrost to retrieve ancient intact Martian organisms, it is necessary to take special precautions to avoid the possibility of contamination. Earth permafrost provides an analog for Martian permafrost and convenient sites for instrument development and field testing. [Copyright &y& Elsevier]

Europa is the closest and probably the most promising target to search for extant life in the Solar System, based on complementary evidence that it may fulfil the key criteria for habitability: the Galileo discovery of a sub-surface ocean; the many indications that the ice shell is active and may be partly permeable to transfer of chemical species, biomolecules and elementary forms of life; the identification of candidate thermal and chemical energy sources necessary to drive a metabolic activity near the ocean floor. In this article we are proposing that ESA collaborates with NASA to design and fly jointly an ambitious and exciting planetary mission, which we call the Joint Europa Mission (JEM), to reach two objectives: perform a full characterization of Europa's habitability with the capabilities of a Europa orbiter, and search for bio-signatures in the environment of Europa (surface, subsurface and exosphere) by the combination of an orbiter and a lander. JEM can build on the advanced understanding of this system which the missions preceding JEM will provide: Juno, JUICE and Europa Clipper, and on the Europa lander concept currently designed by NASA (Maize, report to OPAG, 2019). We propose the following overarching goals for our Joint Europa Mission (JEM): Understand Europa as a complex system responding to Jupiter system forcing, characterize the habitability of its potential biosphere, and search for life at its surface and in its sub-surface and exosphere. We address these goals by a combination of five Priority Scientific Objectives, each with focused measurement objectives providing detailed constraints on the science payloads and on the platforms used by the mission. The JEM observation strategy will combine three types of scientific measurement sequences: measurements on a high-latitude, low-altitude Europan orbit; in-situ measurements to be performed at the surface, using a soft lander; and measurements during the final descent to Europa's surface. The implementation of these three observation sequences will rest on the combination of two science platforms: a soft lander to perform all scientific measurements at the surface and sub-surface at a selected landing site, and an orbiter to perform the orbital survey and descent sequences. We describe a science payload for the lander and orbiter that will meet our science objectives. We propose an innovative distribution of roles for NASA and ESA; while NASA would provide an SLS launcher, the lander stack and most of the mission operations, ESA would provide the carrier-orbiter-relay platform and a stand-alone astrobiology module for the characterization of life at Europa's surface: the Astrobiology Wet Laboratory (AWL). Following this approach, JEM will be a major exciting joint venture to the outer Solar System of NASA and ESA, working together toward one of the most exciting scientific endeavours of the 21st century: to search for life beyond our own planet. • In this article we are proposing that ESA collaborates with NASA to design and fly jointly an ambitious planetary mission: the Joint Europa Mission (JEM). • The JEM observation strategy will combine three types of scientific measurement sequences. • The implementation of these three observation sequences will rest on the combination of two science platforms. • We describe a science payload for the lander and orbiter that will meet our science objectives. • We propose an innovative distribution of roles for NASA and ESA. [ABSTRACT FROM AUTHOR]

Planetary bodies like Mars, Europa, and Enceladus pose the question, "How to study them without contaminating them and destroying future prospects to detect life, if it is there?" The natural trade-off, of course, is that the cleaner your spacecraft, the more you can explore such a body without risk of contaminating it. As chartered by NASA Headquarters, the Planetary Protection Technology Definition Team (PPTDT) was asked to provide a report covering six different areas related to the engineering and technology challenges of implementing planetary protection requirements on solar system exploration missions., (Copyright © 2019 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.)