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Investigations of Jurassic fluvial architecture in central Utah during a three-month simulated Mars surface expedition have revealed a range of expressions of exhumed and inverted relief. They provide tests for prior interpretations of Jurassic fluvial architecture in the area. We propose a new category of exhumed or inverted relief that we term ghost channels. These are landscape ridges that have formed beneath former inverted or exhumed channels where the actual channel facies are no longer present. The formerly present erosion-resistant caps of channel fill have been removed by erosive processes such as parallel scarp retreat. We propose that, when recognised, ghost channels may enable far more complete mapping of former drainage patterns in both landscapes and eroding basins than previously possible. Finally we compare counterparts of these features on the surface of Mars. [ABSTRACT FROM AUTHOR]

In this study, we present quadruple sulfur isotope values (QSI: 32S,33S,34S,36S) measured in sediments from two sulfur-rich Mars analogue environments: i) the glacially-fed hydrothermal pools in Iceland (Kerlingarfjöll and Kverkfjöll), and ii) the Lost Hammer hypersaline spring from Axel Heiberg Island, Nunavut, Canada. The localities host different physical and geochemical characteristics, including aqueous geochemistry, volcanic input, temperature, pH and salinity. The δ34S values of sulfur compounds from the Lost Hammer hypersaline spring exhibit large fractionations typical of microbial sulfate reduction (MSR) with or without additional oxidative sulfur cycling and microbial sulfur disproportionation (MSD) (34ε SO4-CRS from −49.5 to −43.5‰), contrary to the small S isotope fractionations reported for the Icelandic hydrothermal sites (34ε SO4-CRS from −9.9 to −0.7‰). Lost Hammer minor S isotope values (Δ33S and Δ36S), interpreted within the context of a sulfur cycling box model, are consistent with a biogeochemical S cycle including both MSR and MSD. In contrast, the small range in δ34S values within the Iceland hydrothermal pools are consistent with a large volcanic H 2 S flux and minimal biological S cycling. The minor S isotope values recorded in the hydrothermal pools, however, indicate further biogeochemical sulfur cycling. Our results demonstrate that contrasting physical and chemical characteristics between sites support different microbial S cycling processes, as recorded in the QSI sedimentary values. The QSI data and the derived models support the strong potential for QSI values to be used as biosignatures in the search for life in Martian S-rich environments. These results also suggests that extreme, metabolic energy-limited environments with low abiotic sulfur fluxes could be more likely to produce unequivocal biological QSI signals than those with more moderate conditions or abundant available energy. This finding carries significant implications for targeting sites on Mars for in situ measurements or future sample return missions. [ABSTRACT FROM AUTHOR]

Over the past 15 years several expeditions by French, American and especially Italian cavers have unveiled over 50 caves in the Cordillera de la Sal (Atacama Desert, Northern Chile). Many of these caves contain a variety of speleothems and minerals, some of which have rarely been observed within karst systems. Most of the secondary deposits in these caves are composed of halite, but also other halide, carbonate, sulphate, nitrate, phosphate, and silicate minerals have been found. Among the sixteen cave mineral species recognized, atacamite, darapskite, blödite, leonite, anhydrite, and especially antarcticite are worth mentioning. In one of the samples an unknown Ca-Sr-bearing chloride mineral has also been discovered, but it has not been possible to carry out detailed mineralogical analyses. These often-rare minerals have formed in this region due to the very extreme hyperarid and salt-rich environment. This research reports the mineralogical results and proposes the genetical mechanisms leading to the formation of antarcticite, powdery anhydrite, and the paragenesis of the halite-darapskite-blödite. This study also shows that Atacama caves may be excellent analogues to study weathering processes and subsurface secondary minerals in hyperarid and hypersaline environments on Mars.

During field work at the Ibn Battuta Mars analogue sites, two research questions were analyzed: (1) How do we identify sampling sites using remote and local imaging and (2) what kind of information can be gained from shallow subsurface exploration? While remote images help in targeting field activities in general, the connection between observations at different spatial scales for different rocky desert terrain types is not well established; in this, focused comparison of remote in situ images of well-selected analogues would help a great deal. Dried up lake beds as discerned in remotely acquired data may not show signatures of past water activity, while shallow subsurface exploration could reveal the lacustrine period. Acquisition of several satellite images of the same terrain under different geometries would help to support the planning of such in situ work. The selection of appropriate sampling sites in fluvial settings could be improved by analyzing long, meter-high, open-air outcrops that formed during most recent fluvial episodes. Such settings are abundant on Earth and could be present on Mars but may be just below the resolution of available data. By using 20–30-cm-deep excavations, shallow subsurface exploration could reveal the last period of geological history that would have been unattainable by surface observation alone. Aggregates embedded in the original strata or from heavily pulverized samples could not be identified; only weakly fragmented samples viewed right after acquisition showed aggregates, and thus, the Close-Up Imager (CLUPI) on the ExoMover might provide information on cementation-related aggregation on the observing plate before crushing. The mechanical separation of different size grains (mainly clays and attached minerals) would also support the identification of individual components. To maximize context information during subsurface exploration, rover imaging should be accomplished before crushing; however, currently planned imaging may not be ideal for this. [ABSTRACT FROM AUTHOR]

Locations on Earth that provide insights into processes that may be occurring or may have occurred throughout martian history are often broadly deemed "Mars analog environments." As no single locale can precisely represent a past or present martian environment, it is important to focus on characterization of terrestrial processes that produce analogous features to those observed in specific regions of Mars or, if possible, specific time periods during martian history. Here, we report on the preservation of ionic species in soil samples collected from the Tindouf region of Morocco and compare them with the McMurdo Dry Valleys of Antarctica, the Atacama Desert in Chile, the martian meteorite EETA79001, and the in situ Mars analyses from the Phoenix Wet Chemistry Laboratory (WCL). The Moroccan samples show the greatest similarity with those from Victoria Valley, Beacon Valley, and the Atacama, while being consistently depleted compared to University Valley and enriched compared to Taylor Valley. The NO3/Cl ratios are most similar to Victoria Valley and Atacama, while the SO4/Cl ratios are similar to those from Beacon Valley, Victoria Valley, and the Atacama. While perchlorate concentrations in the Moroccan samples are typically lower than those found in samples of other analog sites, conditions in the region are sufficiently arid to retain oxychlorines at detectable levels. Our results suggest that the Tindouf Basin in Morocco can serve as a suitable analogue for the soil geochemistry and subsequent aridification of the Noachian epoch on Mars. [ABSTRACT FROM AUTHOR]

Unambiguous identification of biosignatures on Mars requires access to well-characterized, long-lasting geochemical standards at the planet’s surface that can be modified by theoretical martian life. Ordinary chondrites, which are ancient meteorites that commonly fall to the surface of Mars and Earth, have well-characterized, narrow ranges in trace element and isotope geochemistry compared to martian rocks. Given that their mineralogy is more attractive to known chemolithotrophic life than the basaltic rocks that dominate the martian surface, exogenic rocks (e.g., chondritic meteorites) may be good places to look for signs of prior life endemic to Mars. In this study, we show that ordinary chondrites, collected from the arid Australian Nullarbor Plain, are commonly colonized and inhabited by terrestrial microorganisms that are endemic to this Mars analogue site. These terrestrial endolithic and chasmolithic microbial contaminants are commonly found in close association with hygroscopic veins of gypsum and Mg-calcite, which have formed within cracks penetrating deep into the meteorites. Terrestrial bacteria are observed within corrosion cavities, where troilite (FeS) oxidation has produced jarosite [KFe 3 (SO 4 ) 2 (OH) 6 ]. Where terrestrial microorganisms have colonized primary silicate minerals and secondary calcite, these mineral surfaces are heavily etched. Our results show that inhabitation of meteorites by terrestrial microorganisms in arid environments relies upon humidity and pH regulation by minerals. Furthermore, microbial colonization affects the weathering of meteorites and production of sulfate, carbonate, Fe-oxide and smectite minerals that can preserve chemical and isotopic biosignatures for thousands to millions of years on Earth. Meteorites are thus habitable by terrestrial microorganisms, even under highly desiccating environmental conditions of relevance to Mars. They may therefore be useful as chemical and isotopic “standards” that preserve evidence of life, thereby providing the possibility of universal context for recognition of microbial biosignatures on Earth, Mars and throughout the solar system. [ABSTRACT FROM AUTHOR]

Over the past 15 years several expeditions by French, American and especially Italian cavers have unveiled over 50 caves in the Cordillera de la Sal (Atacama Desert, Northern Chile). Many of these caves contain a variety of speleothems and minerals, some of which have rarely been observed within karst systems. Most of the secondary deposits in these caves are composed of halite, but also other halide, carbonate, sulphate, nitrate, phosphate, and silicate minerals have been found. Among the sixteen cave mineral species recognized, atacamite, darapskite, blödite, leonite, anhydrite, and especially antarcticite are worth mentioning. In one of the samples an unknown Ca-Sr-bearing chloride mineral has also been discovered, but it has not been possible to carry out detailed mineralogical analyses. These often-rare minerals have formed in this region due to the very extreme hyperarid and salt-rich environment. This research reports the mineralogical results and proposes the genetical mechanisms leading to the formation of antarcticite, powdery anhydrite, and the paragenesis of the halite-darapskiteblödite. This study also shows that Atacama caves may be excellent analogues to study weathering processes and subsurface secondary minerals in hyperarid and hypersaline environments on Mars. [ABSTRACT FROM AUTHOR]

This study reports the environmental conditions of temperature, moisture and radiation for four years (May 2004 to July 2008) in the area known as Pampas de La Joya in southern Peru, which recently has been considered as a new Mars analogue. The period of evaluation includes the El Niño Southern Oscillation (ENSO) during the months of September 2006 to March 2007, which, despite not having catastrophic effects like its predecessor on 1997–1998, showed an interesting increase in humidity. Our data describe the extreme conditions present in the region and their relationship with the presence of potential habitats that could allow for the survival of micro-organisms. The average environmental temperature was 18.9°C, with a maximum of 35.9°C and a minimum of −4.5°C. The annual average incident solar radiation was 508 W m−2, with high near 1060 W m−2 at noon during the driest period between September and March. The average relative humidity (RH) was 29.5, 20.1 and 20.4% for air, soil and rock, respectively. The RH had higher values at night due to fog during the months of June and August, and during the early morning between December and March. During the months of ENSO event there were four episodes of precipitation (1.1, 1.5, 2.0 and 0.9 mm), of which three increased soil and rock moisture on an average more than 45% and persisted for over 15 days after precipitation, while the atmospheric environment had no significant variations. Finally, quartz rocks and evaporite minerals colonized with micro-organisms were found as the only micro-habitats, in this region, capable of supporting life in this extreme environment. [ABSTRACT FROM PUBLISHER]

Several space agencies and exploration stakeholders have a strong interest in obtaining information on technical and human aspects to prepare for future extra-terrestrial planetary exploration. In this context, the EuroGeoMars campaign, organized with support from the International Lunar Exploration Working Group (ILEWG), the European Space Agency (ESA), the National Aeronautics and Space Administration (NASA) Ames Research Center and partner institutes, was conducted by the crews 76 and 77 in February 2009 in The Mars Society's ‘Mars Desert Research Station’ (MDRS) in Utah.The EuroGeoMars encompasses two groups of experiments: (1) a series of field science experiments that can be conducted from an extra-terrestrial planetary surface in geology, biology, astronomy/astrophysics and the necessary technology and networks to support these field investigations; (2) a series of human crew-related investigations on crew time organization in a planetary habitat, on the different functions and interfaces of this habitat, and on man–machine interfaces of science and technical equipment.This paper recalls the objective of the EuroGeoMars project and presents the MDRS and its habitat layout. Social and operational aspects during simulations are described. Technical and operational aspects of biology investigations in the field and in the habitat laboratory are discussed in detail with the focus point set on the polymerase chain reaction (PCR)-based detection of microbial DNA in soil samples. [ABSTRACT FROM AUTHOR]

Abstract: Australia is an ideal testing ground in preparation for the robotic and human exploration of Mars. Numerous sites with landforms or processes analogous to those on Mars are present and the deserts of central Australia provide a range of locations for free-ranging Mars analogue mission simulations. The latest developments in testing technologies and strategies for exploration in Australian Mars analogues are reviewed. These include trials of analogue space suits based on mechanical counter pressure technology and the development of an analogue, crewed, pressurized rover for long-range exploration. Field science activities and instrumentation testing relevant to robotic and future crewed missions are discussed. Australian-led human factors research undertaken during expeditions to Mars analogue research stations and expeditions to Antarctica are also reviewed. Education and public outreach activities related to Mars analogue research in Australia are also detailed. [Copyright &y& Elsevier]

Abstract: Australia has numerous landforms and features, some unique, that provide a useful reference for interpreting the results of spacecraft orbiting Mars and exploring the martian surface. Examples of desert landforms, impact structures, relief inversion, long-term landscape evolution and hydrothermal systems that are relevant to Mars are outlined and the relevant literature reviewed. The Mars analogue value of Australia''s acid lakes, hypersaline embayments and mound spring complexes is highlighted along with the Pilbara region, where the oldest convincing evidence of life guides exploration for early life on Mars. The distinctive characteristics of the Arkaroola Mars Analogue Region are also assessed and opportunities for future work in Australia are outlined. [Copyright &y& Elsevier]

Layered mounds and inverted channels with polygonal fractures from the Ntwetwe Pan in the Makgadikgadi Basin (central Botswana) have been herein investigated. These morphologies are from an evaporitic basin (the Makgadikgadi Basin) that is the remnant of an ancient Pleistocene lake and is currently part of the world's largest evaporitic system. The mounds in the Ntwetwe Pan are characterized by a layered structure and low relief (max. 5 m above the pan floor) and can be in excess of 2 ​km wide. The mounds consist mainly of loose (non-lithified) sand and silt with high moisture contents, even during the dry season. Geophysical investigations have shown that groundwater processes, particularly those related to the capillary fringe that rises and conveys moisture through the mounds, are factors that make mound sediments resistant to wind erosion. The inverted channels, identified in the southern part of the Ntwetwe Pan, are characterized by gentle reliefs and depressions, which depend upon the distribution of calcretes and indurated sediments. Large scale (up to 100 ​m wide) polygonal fractures localized at the front of the channels, disappear at the transition with the present-day pan floor. We consider that these particular mounds, within the Ntwetwe Pan, are remnants of the strandline of the paleo-Makgadikgadi Lake, and that the inverted channels represent distributary channels of a relict fan delta, formed by an ephemeral river, most likely the paleo-Boteti River, during a Lake Paleo-Makgadikgadi highstand stage. We consider that large scale (up to 100 ​m wide) polygonal fractures, located on the channel-mouth lobes, represent large-scale desiccation cracks formed by rapid water evaporation from delta deposits. The results of this investigation highlight the importance of the paleo-drainage system and its interactions with the water table and wind-deflation as main geomorphological factors within salt pan environments. The mounds in the Makgadikgadi pans also show strong geomorphic similarities to spring mounds on the surface of Mars, localized in equatorial layered deposits (ELDs). These ELDs mounds are considered to result from cyclical groundwater upwelling, evaporation and wind deflation. The geological processes that resulted in the formation of mounds within the Makgadikgadi pans may, therefore, help to explain how similar layered deposits formed on Mars and confirm existing theories. • Mounds, inverted channels and polygons from the Ntwetwe pan have been investigated. • The mounds are layered remnants of the deposits of a giant paleolake. • The interaction between rising water table and erosion created these mounds. • These morphologies are considered analogues of the ELDs on Mars. • The processes active in the Ntwetwe pan can shed light on Martian ELDs genesis. [ABSTRACT FROM AUTHOR]