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Abstract
Recurring Slope Lineae (RSL) on Mars have been enigmatic since their discovery; their behavior resembles a seeping liquid but sources of water remain puzzling. This work demonstrates that the properties of RSL are consistent with observed behaviors of Martian and terrestrial aeolian processes. Specifically, RSL are well-explained as flows of sand that remove a thin coating of dust. Observed RSL properties are supportive of or consistent with this model, which requires no liquid water or other exotic processes, but rather indicates seasonal aeolian behavior. These settings and behaviors resemble features observed by rovers and also explain the occurrence of many slope lineae on Mars that do not meet the strict definition of RSL. This indicates that RSL can be explained simply as aeolian features. Other processes may add complexities just as they could modify the behavior of any sand dune.
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Affiliation(s)
- Colin M. Dundas
- U.S. Geological Survey, Astrogeology Science Center, 2255 N. Gemini Dr., Flagstaff, AZ 86001, USA
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2
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Kereszturi Á. Unique and Potentially Mars-Relevant Flow Regime and Water Sources at a High Andes-Atacama Site. ASTROBIOLOGY 2020; 20:723-740. [PMID: 32525739 DOI: 10.1089/ast.2018.2013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
A field expedition in the High Andes/Atacama Desert region revealed two types of flow-produced structures and a unique flow regime. Gullies somewhat smaller than those on Mars (width: 0.2-1 m, depth: 0.2-0.6 m, length: 4-60 m) were observed as mainly erosional structures. The other flow-related feature called infilled valleys showed activity only in specific, spatially discrete areas during the daytime. The active sections were composed of a source depression where liquid H2O was produced from subsurface buried sources, which flowed down and percolated into fine-grained infilling material of the valley. Several such active sections could be present along one valley, separated by inactive ones. Three types of H2O sources fed them: buried snow, surface snow, and ice left behind from the liquid water that had emerged the preceding day. This latter source has not yet been suggested for Mars. Some aspects related to the formation of the gullies and infilled valleys (H2O budget, albedo, erosional processes) may be similar with the formation processes hypothesized for the recurring slope lineae on Mars. The observed diurnal spatially discrete activity of the infilled valleys is related to the interaction of insolation and mass movement of exhumed subsurface snow, which is also believed to exist on Mars. The Ojos del Salado site is unique in that, despite it being located in the hyperarid High Andes/Atacama Desert region, material from rare snowfall events has been protected due to burial by grains transported by strong winds, supporting ephemeral melting in the long term.
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Affiliation(s)
- Ákos Kereszturi
- Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklos Astronomical Institute, Budapest, Hungary
- European Astrobiology Institute, Strasbourg, France
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3
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Nair CPR, Unnikrishnan V. Stability of the Liquid Water Phase on Mars: A Thermodynamic Analysis Considering Martian Atmospheric Conditions and Perchlorate Brine Solutions. ACS OMEGA 2020; 5:9391-9397. [PMID: 32363291 PMCID: PMC7191838 DOI: 10.1021/acsomega.0c00444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 03/27/2020] [Indexed: 05/17/2023]
Abstract
The stability of the liquid water phase on Mars has been examined on the basis of fundamental thermodynamic principles. The analysis considers the atmospheric pressure and temperature conditions prevalent on Mars. Because of the very low atmospheric pressure on Mars, water cannot exist in the liquid form. However, salt dissolution can reduce the freezing point and elevate the boiling point of aqueous solutions. This is interesting in the light of the discovery of perchlorate, sulphate, sodium, potassium, and calcium ions over the Martian surface. The effect of different perchlorate salts on the freezing and boiling points of water while considering their saturation solubility under varying ionic conditions is key to this analysis. It is shown that under an average atmospheric pressure of 600 Pa, the saturated solution of sodium perchlorate (NaClO4) is stable in the liquid phase in the temperature range between 240 and 275 K. The triple point of water under this condition is shifted to 269 K with a saturation solubility of 14.4 mass % of the salt. However, a saturated solution of magnesium perchlorate (Mg(ClO4)2) renders this temperature range wider from 198 to 296 K, with the triple point being located at 269 K (salt saturation at 13.5 mass % salt). In case the water is contaminated with a mixture of these salts, an increased stability is predicted for liquid water down to 180 K and up to at least 298 K. This is caused by the increased ionic strength that enhances the freezing point depression and boiling point elevation of the solution. Thus, in the extreme and uneventful conditions of saturation by mixtures of salts, liquid water can be stable on Mars between 180 K and at least up to 298 K. Below this temperature, water exists as a glacier and above, as steam only.
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Affiliation(s)
- C. P. Reghunadhan Nair
- Propellants,
Polymers, Chemicals & Materials Entity (PCM), Vikram Sarabhai Space Center, Thiruvananthapuram 695022, Kerala, India
- . Phone: 91 484 2862378. Fax: 91 484 2577747
| | - Vibhu Unnikrishnan
- Application
Development Division, Chemical Systems Group, Propellants, Polymers,
Chemicals & Materials Entity (PCM), Vikram Sarabhai Space Center, Thiruvananthapuram 695022, Kerala, India
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4
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Shotwell RF, Hays LE, Beaty DW, Goreva Y, Kieft TL, Mellon MT, Moridis G, Peterson LD, Spycher N. Can an Off-Nominal Landing by an MMRTG-Powered Spacecraft Induce a Special Region on Mars When No Ice Is Present? ASTROBIOLOGY 2019; 19:1315-1338. [PMID: 31657948 DOI: 10.1089/ast.2017.1688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
This work aims at addressing whether a catastrophic failure of an entry, descent, and landing event of a Multimission Radioisotope Thermoelectric Generator-based lander could embed the heat sources into the martian subsurface and create a local environment that (1) would temporarily satisfy the conditions for a martian Special Region and (2) could establish a transport mechanism through which introduced terrestrial organisms could be mobilized to naturally occurring Special Regions elsewhere on Mars. Two models were run, a primary model by researchers at the Lawrence Berkeley National Laboratory and a secondary model by researchers at the Jet Propulsion Laboratory, both of which were based on selected starting conditions for various surface composition cases that establish the worst-case scenario, including geological data collected by the Mars Science Laboratory at Gale Crater. The summary outputs of both modeling efforts showed similar results: that the introduction of the modeled heat source could temporarily create the conditions established for a Special Region, but that there would be no transport mechanism by which an introduced terrestrial microbe, even if it was active during the temporarily induced Special Region conditions, could be transported to a naturally occurring Special Region of Mars.
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Affiliation(s)
- Robert F Shotwell
- Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - Lindsay E Hays
- Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - David W Beaty
- Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - Yulia Goreva
- Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
| | - Thomas L Kieft
- Biology Department, New Mexico Tech, Socorro, New Mexico
| | - Michael T Mellon
- The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland
| | - George Moridis
- Lawrence Berkeley National Laboratory, Berkeley, California
| | - Lee D Peterson
- Jet Propulsion Laboratory/California Institute of Technology, Pasadena, California
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Dundas CM, Mellon MT, Conway SJ, Gastineau R. Active Boulder Movement at High Martian Latitudes. GEOPHYSICAL RESEARCH LETTERS 2019; 46:5075-5082. [PMID: 31423033 PMCID: PMC6686660 DOI: 10.1029/2019gl082293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/04/2019] [Accepted: 04/22/2019] [Indexed: 06/10/2023]
Abstract
Lobate stony landforms occur on steep slopes at high latitudes on Mars. We demonstrate active boulder movement at seven such sites. Submeter-scale boulders frequently move distances of a few meters. The movement is concentrated in the vicinity of the lobate landforms but also occurs on other slopes. This provides evidence for a newly discovered, common style of activity on Mars, which may play an important role in slope degradation. It also opens the possibility that the lobate features are currently forming in the absence of significant volumes of liquid water.
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Affiliation(s)
- Colin M. Dundas
- U.S. Geological SurveyAstrogeology Science CenterFlagstaffAZUSA
| | - Michael T. Mellon
- Center for Astrophysics and Planetary ScienceCornell UniversityIthacaNYUSA
| | - Susan J. Conway
- CNRS UMR6112 Laboratoire de Planétologie et Géodynamique, Université de NantesNantesFrance
| | - Renaldo Gastineau
- CNRS UMR6112 Laboratoire de Planétologie et Géodynamique, Université de NantesNantesFrance
- Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerreGrenobleFrance
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Abotalib AZ, Heggy E. A deep groundwater origin for recurring slope lineae on Mars. NATURE GEOSCIENCE 2019; 12:235-241. [PMID: 30949231 PMCID: PMC6443380 DOI: 10.1038/s41561-019-0327-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Accepted: 02/13/2019] [Indexed: 06/01/2023]
Affiliation(s)
- Abotalib Z. Abotalib
- University of Southern California, Viterbi School of Engineering, Los Angeles, CA, 90089
- National Authority for Remote Sensing and Space Sciences, Department of Geological Applications, Cairo, 1564, Egypt
| | - Essam Heggy
- University of Southern California, Viterbi School of Engineering, Los Angeles, CA, 90089
- Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA, 91109-8001, USA
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Stevens AH, Childers D, Fox-Powell M, Nicholson N, Jhoti E, Cockell CS. Growth, Viability, and Death of Planktonic and Biofilm Sphingomonas desiccabilis in Simulated Martian Brines. ASTROBIOLOGY 2019; 19:87-98. [PMID: 30048150 PMCID: PMC6338574 DOI: 10.1089/ast.2018.1840] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 06/12/2018] [Indexed: 05/22/2023]
Abstract
Aqueous solutions on Mars are theorized to contain very different ion compositions than those on Earth. To determine the effect of such solutions on typical environmental micro-organisms, which could be released from robotic spacecraft or human exploration activity, we investigated the resistance of Sphingomonas desiccabilis to brines that simulate the composition of martian aqueous environments. S. desiccabilis is a desiccation-resistant, biofilm-forming microbe found in desert crusts. The viability of cells in both planktonic and biofilm forms was measured after exposure to simulated martian brines. Planktonic cells showed a loss of viability over the course of several hours in almost all of the seven brines tested. Biofilms conferred greater resistance to all the brines, including those with low water activity and pH, but even cells in biofilms showed a complete loss of viability in <6 h in the harsher brines and in <2 days in the less harsh brines. One brine, however, allowed the microbes to maintain viability over several days, despite having a water activity and pH lower and ionic strength higher than brines that reduced viability over the same timescales, suggesting important ion-specific effects. These data show that biofilm-forming cells have a greater capacity to resist martian aqueous extremes, but that evaporative or deliquescent brines are likely to be destructive to many organisms over relatively short timescales, with implications for the habitability of Mars and for micro-organisms dispersed by robotic or human explorers.
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Affiliation(s)
- Adam H. Stevens
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Delma Childers
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
- Aberdeen Fungal Group, Institute of Medical Sciences, MRC Centre for Medical Mycology at the University of Aberdeen, Aberdeen, United Kingdom
| | - Mark Fox-Powell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
- School of Earth and Environmental Sciences, University of St. Andrews, St. Andrews, United Kingdom
| | - Natasha Nicholson
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Elisha Jhoti
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
| | - Charles S. Cockell
- UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom
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8
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Mickol RL, Laird SK, Kral TA. Non-Psychrophilic Methanogens Capable of Growth Following Long-Term Extreme Temperature Changes, with Application to Mars. Microorganisms 2018; 6:microorganisms6020034. [PMID: 29690617 PMCID: PMC6027200 DOI: 10.3390/microorganisms6020034] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Revised: 04/13/2018] [Accepted: 04/16/2018] [Indexed: 01/25/2023] Open
Abstract
Although the martian environment is currently cold and dry, geomorphological features on the surface of the planet indicate relatively recent (<4 My) freeze/thaw episodes. Additionally, the recent detections of near-subsurface ice as well as hydrated salts within recurring slope lineae suggest potentially habitable micro-environments within the martian subsurface. On Earth, microbial communities are often active at sub-freezing temperatures within permafrost, especially within the active layer, which experiences large ranges in temperature. With warming global temperatures, the effect of thawing permafrost communities on the release of greenhouse gases such as carbon dioxide and methane becomes increasingly important. Studies examining the community structure and activity of microbial permafrost communities on Earth can also be related to martian permafrost environments, should life have developed on the planet. Here, two non-psychrophilic methanogens, Methanobacterium formicicum and Methanothermobacter wolfeii, were tested for their ability to survive long-term (~4 year) exposure to freeze/thaw cycles varying in both temperature and duration, with implications both for climate change on Earth and possible life on Mars.
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Affiliation(s)
- Rebecca L Mickol
- Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
- American Society for Engineering Education, Washington, DC 20036, USA.
| | - Sarah K Laird
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
| | - Timothy A Kral
- Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
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9
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Williams KE, Heldmann JL, McKay CP, Mellon MT. The effects of snow and salt on ice table stability in University Valley, Antarctica. ANTARCTIC SCIENCE 2018; 30:67-78. [PMID: 32818010 PMCID: PMC7430506 DOI: 10.1017/s0954102017000402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The Antarctic Dry Valleys represent a unique environment where it is possible to study dry permafrost overlaying an ice-rich permafrost. In this paper, two opposing mechanisms for ice table stability in University Valley are addressed: i) diffusive recharge via thin seasonal snow deposits andii) desiccation via salt deposits in the upper soil column. A high-resolution time-marching soil and snow model was constructed and applied to University Valley, driven by meteorological station atmospheric measurements. It was found that periodic thin surficial snow deposits (observed in University Valley) are capable of drastically slowing (if not completely eliminating) the underlying ice table ablation. The effects of NaCl, CaCl2 and perchlorate deposits were then modelled. Unlike the snow cover, however, the presence of salt in the soil surface (but no periodic snow) results in a slight increase in the ice table recession rate, due to the hygroscopic effects of salt sequestering vapour from the ice table below. Near-surface pore ice frequently forms when large amounts of salt are present in the soil due to the suppression of the saturation vapour pressure. Implications for Mars high latitudes are discussed.
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Affiliation(s)
- K E Williams
- Montana State University, Department of Earth Sciences, Bozeman, MT 59717, USA
- US Geological Survey, Astrogeology Science Center, Flagstaff, AZ 86001, USA
| | - J L Heldmann
- NASA Ames Research Center, Division of Space Sciences and Astrobiology, Moffett Field, CA 94035, USA
| | - Christopher P McKay
- NASA Ames Research Center, Division of Space Sciences and Astrobiology, Moffett Field, CA 94035, USA
| | - Michael T Mellon
- Johns Hopkins University Applied Physics Laboratory, Planetary Exploration Group, Laurel, MD 20723, USA
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10
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Raack J, Conway SJ, Herny C, Balme MR, Carpy S, Patel MR. Water induced sediment levitation enhances downslope transport on Mars. Nat Commun 2017; 8:1151. [PMID: 29075001 PMCID: PMC5658360 DOI: 10.1038/s41467-017-01213-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Accepted: 08/30/2017] [Indexed: 11/12/2022] Open
Abstract
On Mars, locally warm surface temperatures (~293 K) occur, leading to the possibility of (transient) liquid water on the surface. However, water exposed to the martian atmosphere will boil, and the sediment transport capacity of such unstable water is not well understood. Here, we present laboratory studies of a newly recognized transport mechanism: “levitation” of saturated sediment bodies on a cushion of vapor released by boiling. Sediment transport where this mechanism is active is about nine times greater than without this effect, reducing the amount of water required to transport comparable sediment volumes by nearly an order of magnitude. Our calculations show that the effect of levitation could persist up to ~48 times longer under reduced martian gravity. Sediment levitation must therefore be considered when evaluating the formation of recent and present-day martian mass wasting features, as much less water may be required to form such features than previously thought. Downslope sediment transport on Mars is reported, but the transport capacity of unstable water under low pressures is not well understood. Here, the authors present a newly discovered, highly reactive transportation mechanism that is only possible under low pressure environments.
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Affiliation(s)
- Jan Raack
- School of Physical Sciences, Faculty of Science, Technology, Engineering & Mathematics, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.
| | - Susan J Conway
- Laboratoire de Planétologie et Géodynamique-UMR CNRS 6112, Université de Nantes, 2 rue de la Houssinière-BP 92208, 44322, Nantes Cedex 3, France
| | - Clémence Herny
- Physikalisches Institut, Universität Bern, Sidlerstrasse 5, 3012, Bern, Switzerland
| | - Matthew R Balme
- School of Physical Sciences, Faculty of Science, Technology, Engineering & Mathematics, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK
| | - Sabrina Carpy
- Laboratoire de Planétologie et Géodynamique-UMR CNRS 6112, Université de Nantes, 2 rue de la Houssinière-BP 92208, 44322, Nantes Cedex 3, France
| | - Manish R Patel
- School of Physical Sciences, Faculty of Science, Technology, Engineering & Mathematics, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK.,Space Science and Technology Department, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot, OX11 0QX, UK
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Mangold N, Mangeney A, Migeon V, Ansan V, Lucas A, Baratoux D, Bouchut F. Sinuous gullies on Mars: Frequency, distribution, and implications for flow properties. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003540] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Nunes DC, Smrekar SE, Safaeinili A, Holt J, Phillips RJ, Seu R, Campbell B. Examination of gully sites on Mars with the shallow radar. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003509] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Ulrich R, Kral T, Chevrier V, Pilgrim R, Roe L. Dynamic temperature fields under Mars landing sites and implications for supporting microbial life. ASTROBIOLOGY 2010; 10:643-650. [PMID: 20735254 DOI: 10.1089/ast.2010.0472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
While average temperatures on Mars may be too low to support terrestrial life-forms or aqueous liquids, diurnal peak temperatures over most of the planet can be high enough to provide for both, down to a few centimeters beneath the surface for some fraction of the time. A thermal model was applied to the Viking 1, Viking 2, Pathfinder, Spirit, and Opportunity landing sites to demonstrate the dynamic temperature fields under the surface at these well-characterized locations. A benchmark temperature of 253 K was used as a lower limit for possible metabolic activity, which corresponds to the minimum found for specific terrestrial microorganisms. Aqueous solutions of salts known to exist on Mars can provide liquid solutions well below this temperature. Thermal modeling has shown that 253 K is reached beneath the surface at diurnal peak heating for at least some parts of the year at each of these landing sites. Within 40 degrees of the equator, 253 K beneath the surface should occur for at least some fraction of the year; and, within 20 degrees , it will be seen for most of the year. However, any life-form that requires this temperature to thrive must also endure daily excursions to far colder temperatures as well as periods of the year where 253 K is never reached at all.
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Affiliation(s)
- Richard Ulrich
- Department of Chemical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA.
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Parsons RA, Nimmo F. Numerical modeling of Martian gully sediment transport: Testing the fluvial hypothesis. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003517] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Niederberger TD, Perreault NN, Lawrence JR, Nadeau JL, Mielke RE, Greer CW, Andersen DT, Whyte LG. Novel sulfur-oxidizing streamers thriving in perennial cold saline springs of the Canadian high Arctic. Environ Microbiol 2009; 11:616-29. [DOI: 10.1111/j.1462-2920.2008.01833.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Banks ME, McEwen AS, Kargel JS, Baker VR, Strom RG, Mellon MT, Gulick VC, Keszthelyi L, Herkenhoff KE, Pelletier JD, Jaeger WL. High Resolution Imaging Science Experiment (HiRISE) observations of glacial and periglacial morphologies in the circum-Argyre Planitia highlands, Mars. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je002994] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Mellon MT, Arvidson RE, Marlow JJ, Phillips RJ, Asphaug E. Periglacial landforms at the Phoenix landing site and the northern plains of Mars. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je003039] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Formation of gullies on Mars: link to recent climate history and insolation microenvironments implicate surface water flow origin. Proc Natl Acad Sci U S A 2008; 105:13258-63. [PMID: 18725636 DOI: 10.1073/pnas.0803760105] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Features seen in portions of a typical midlatitude Martian impact crater show that gully formation follows a geologically recent period of midlatitude glaciation. Geological evidence indicates that, in the relatively recent past, sufficient snow and ice accumulated on the pole-facing crater wall to cause glacial flow and filling of the crater floor with debris-covered glaciers. As glaciation waned, debris-covered glaciers ceased flowing, accumulation zones lost ice, and newly exposed wall alcoves continued as the location for limited snow/frost deposition, entrapment, and preservation. Analysis of the insolation geometry of this pole-facing crater wall, and similar occurrences in other craters at these latitudes on Mars, shows that they are uniquely favored for accumulation of snow and ice, and a relatively more rapid exposure to warmer summer temperatures. We show that, after the last glaciation, melting of residual snow and ice in alcoves could have formed the fluvial channels and sedimentary fans of the gullies. Recent modeling shows that top-down melting can occur in these microenvironments under conditions similar to those currently observed on Mars, if small amounts of snow or frost accumulate in alcoves and channels. Accumulation and melting is even more favored in the somewhat wetter, relatively recent geological past of Mars, after the period of active glaciation.
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Piqueux S, Christensen PR. North and south subice gas flow and venting of the seasonal caps of Mars: A major geomorphological agent. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je003009] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Fernández-Remolar DC, Gómez F, Prieto-Ballesteros O, Schelble RT, Rodríguez N, Amils R. Some ecological mechanisms to generate habitability in planetary subsurface areas by chemolithotrophic communities: the Río Tinto subsurface ecosystem as a model system. ASTROBIOLOGY 2008; 8:157-173. [PMID: 18237256 DOI: 10.1089/ast.2006.0022] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Chemolithotrophic communities that colonize subsurface habitats have great relevance for the astrobiological exploration of our Solar System. We hypothesize that the chemical and thermal stabilization of an environment through microbial activity could make a given planetary region habitable. The MARTE project ground-truth drilling campaigns that sampled cryptic subsurface microbial communities in the basement of the Río Tinto headwaters have shown that acidic surficial habitats are the result of the microbial oxidation of pyritic ores. The oxidation process is exothermic and releases heat under both aerobic and anaerobic conditions. These microbial communities can maintain the subsurface habitat temperature through storage heat if the subsurface temperature does not exceed their maximum growth temperature. In the acidic solutions of the Río Tinto, ferric iron acts as an effective buffer for controlling water pH. Under anaerobic conditions, ferric iron is the oxidant used by microbes to decompose pyrite through the production of sulfate, ferrous iron, and protons. The integration between the physical and chemical processes mediated by microorganisms with those driven by the local geology and hydrology have led us to hypothesize that thermal and chemical regulation mechanisms exist in this environment and that these homeostatic mechanisms could play an essential role in creating habitable areas for other types of microorganisms. Therefore, searching for the physicochemical expression of extinct and extant homeostatic mechanisms through physical and chemical anomalies in the Mars crust (i.e., local thermal gradient or high concentration of unusual products such as ferric sulfates precipitated out from acidic solutions produced by hypothetical microbial communities) could be a first step in the search for biological traces of a putative extant or extinct Mars biosphere.
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Cabrol NA, Wettergreen D, Warren-Rhodes K, Grin EA, Moersch J, Diaz GC, Cockell CS, Coppin P, Demergasso C, Dohm JM, Ernst L, Fisher G, Glasgow J, Hardgrove C, Hock AN, Jonak D, Marinangeli L, Minkley E, Ori GG, Piatek J, Pudenz E, Smith T, Stubbs K, Thomas G, Thompson D, Waggoner A, Wagner M, Weinstein S, Wyatt M. Life in the Atacama: Searching for life with rovers (science overview). ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006jg000298] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Nathalie A. Cabrol
- Space Sciences Division; NASA Ames Research Center; Moffett Field California USA
- SETI Institute; Mountain View California USA
| | - David Wettergreen
- Robotics Institute; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Kim Warren-Rhodes
- Space Sciences Division; NASA Ames Research Center; Moffett Field California USA
- SETI Institute; Mountain View California USA
| | - Edmond A. Grin
- Space Sciences Division; NASA Ames Research Center; Moffett Field California USA
- SETI Institute; Mountain View California USA
| | - Jeffrey Moersch
- Department of Earth and Planetary Sciences; University of Tennessee; Knoxville Tennessee USA
| | | | - Charles S. Cockell
- Planetary and Space Sciences Research Institute; Open University; Milton Keynes UK
| | - Peter Coppin
- Robotics Institute; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | | | - James M. Dohm
- Hydrology and Water Resources Department; University of Arizona; Tucson Arizona USA
| | - Lauren Ernst
- Department of Biology; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Gregory Fisher
- Department of Biology; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Justin Glasgow
- Department of Industrial Engineering; University of Iowa; Iowa City Iowa USA
| | - Craig Hardgrove
- Department of Earth and Planetary Sciences; University of Tennessee; Knoxville Tennessee USA
| | - Andrew N. Hock
- Department of Earth and Space Sciences; University of California; Los Angeles California USA
| | - Dominic Jonak
- Robotics Institute; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | | | - Edwin Minkley
- Department of Biology; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | | | - Jennifer Piatek
- Department of Earth and Planetary Sciences; University of Tennessee; Knoxville Tennessee USA
| | - Erin Pudenz
- Department of Industrial Engineering; University of Iowa; Iowa City Iowa USA
| | - Trey Smith
- Robotics Institute; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Kristen Stubbs
- Robotics Institute; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Geb Thomas
- Department of Industrial Engineering; University of Iowa; Iowa City Iowa USA
| | - David Thompson
- Robotics Institute; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Alan Waggoner
- Department of Biology; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Michael Wagner
- Robotics Institute; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Shmuel Weinstein
- Department of Biology; Carnegie Mellon University; Pittsburgh Pennsylvania USA
| | - Michael Wyatt
- Department of Earth and Planetary Sciences; University of Tennessee; Knoxville Tennessee USA
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23
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Minitti ME, Weitz CM, Lane MD, Bishop JL. Morphology, chemistry, and spectral properties of Hawaiian rock coatings and implications for Mars. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006je002839] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Malin MC, Bell JF, Cantor BA, Caplinger MA, Calvin WM, Clancy RT, Edgett KS, Edwards L, Haberle RM, James PB, Lee SW, Ravine MA, Thomas PC, Wolff MJ. Context Camera Investigation on board the Mars Reconnaissance Orbiter. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2006je002808] [Citation(s) in RCA: 805] [Impact Index Per Article: 47.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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25
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McEwen AS, Eliason EM, Bergstrom JW, Bridges NT, Hansen CJ, Delamere WA, Grant JA, Gulick VC, Herkenhoff KE, Keszthelyi L, Kirk RL, Mellon MT, Squyres SW, Thomas N, Weitz CM. Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE). ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2005je002605] [Citation(s) in RCA: 1056] [Impact Index Per Article: 62.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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26
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Abstract
Application of physical and chemical concepts, complemented by studies of prokaryotes in ice cores and permafrost, has led to the present understanding of how microorganisms can metabolize at subfreezing temperatures on Earth and possibly on Mars and other cold planetary bodies. The habitats for life at subfreezing temperatures benefit from two unusual properties of ice. First, almost all ionic impurities are insoluble in the crystal structure of ice, which leads to a network of micron-diameter veins in which microorganisms may utilize ions for metabolism. Second, ice in contact with mineral surfaces develops a nanometre-thick film of unfrozen water that provides a second habitat that may allow microorganisms to extract energy from redox reactions with ions in the water film or ions in the mineral structure. On the early Earth and on icy planets, prebiotic molecules in veins in ice may have polymerized to RNA and polypeptides by virtue of the low water activity and high rate of encounter with each other in nearly one-dimensional trajectories in the veins. Prebiotic molecules may also have utilized grain surfaces to increase the rate of encounter and to exploit other physicochemical features of the surfaces.
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Affiliation(s)
- P Buford Price
- Physics Department, University of California, Berkeley, CA 94720, USA.
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27
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Malin MC, Edgett KS, Posiolova LV, McColley SM, Dobrea EZN. Present-day impact cratering rate and contemporary gully activity on Mars. Science 2006; 314:1573-7. [PMID: 17158321 DOI: 10.1126/science.1135156] [Citation(s) in RCA: 397] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The Mars Global Surveyor Mars Orbiter Camera has acquired data that establish the present-day impact cratering rate and document new deposits formed by downslope movement of material in mid-latitude gullies on Mars. Twenty impacts created craters 2 to 150 meters in diameter within an area of 21.5 x 10(6) square kilometers between May 1999 and March 2006. The values predicted by models that scale the lunar cratering rate to Mars are close to the observed rate, implying that surfaces devoid of craters are truly young and that as yet unrecognized processes of denudation must be operating. The new gully deposits, formed since August 1999, are light toned and exhibit attributes expected from emplacement aided by a fluid with the properties of liquid water: relatively long, extended, digitate distal and marginal branches, diversion around obstacles, and low relief. The observations suggest that liquid water flowed on the surface of Mars during the past decade.
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Affiliation(s)
- Michael C Malin
- Malin Space Science Systems, Post Office Box 910148, San Diego, CA 92191-0148, USA
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28
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Taylor GJ, Stopar JD, Boynton WV, Karunatillake S, Keller JM, Brückner J, Wänke H, Dreibus G, Kerry KE, Reedy RC, Evans LG, Starr RD, Martel LMV, Squyres SW, Gasnault O, Maurice S, d'Uston C, Englert P, Dohm JM, Baker VR, Hamara D, Janes D, Sprague AL, Kim KJ, Drake DM, McLennan SM, Hahn BC. Variations in K/Th on Mars. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2006je002676] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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29
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Prieto-Ballesteros O, Fernández-Remolar DC, Rodríguez-Manfredi JA, Selsis F, Manrubia SC. Spiders: water-driven erosive structures in the southern hemisphere of Mars. ASTROBIOLOGY 2006; 6:651-67. [PMID: 16916289 DOI: 10.1089/ast.2006.6.651] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Recent data from space missions reveal that there are ongoing climatic changes and erosive processes that continuously modify surface features of Mars. We have investigated the seasonal dynamics of a number of morphological features located at Inca City, a representative area at high southern latitude that has undergone seasonal processes. By integrating visual information from the Mars Orbiter Camera on board the Mars Global Surveyor and climatic cycles from a Mars' General Circulation Model, and considering the recently reported evidence for the presence of water-ice and aqueous precipitates on Mars, we propose that a number of the erosive features identified in Inca City, among them spiders, result from the seasonal melting of aqueous salty solutions.
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Affiliation(s)
- Olga Prieto-Ballesteros
- Centro de Astrobiología, Instituto Nacional de Técnica Aeroespacial-Consejo Superior de Investigaciones Científicas, Ctra. Ajalvir km. 4, 28850 Torrejón de Ardoz, Madrid, Spain.
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30
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Balme M, Mangold N, Baratoux D, Costard F, Gosselin M, Masson P, Pinet P, Neukum G. Orientation and distribution of recent gullies in the southern hemisphere of Mars: Observations from High Resolution Stereo Camera/Mars Express (HRSC/MEX) and Mars Orbiter Camera/Mars Global Surveyor (MOC/MGS) data. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002607] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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31
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Tung HC, Bramall NE, Price PB. Microbial origin of excess methane in glacial ice and implications for life on Mars. Proc Natl Acad Sci U S A 2005; 102:18292-6. [PMID: 16339015 PMCID: PMC1308353 DOI: 10.1073/pnas.0507601102] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Methane trapped in the 3,053-m-deep Greenland Ice Sheet Project 2 ice core provides an important record of millennial-scale climate change over the last 110,000 yr. However, at several depths in the lowest 90 m of the ice core, the methane concentration is up to an order of magnitude higher than at other depths. At those depths we have discovered methanogenic archaea, the in situ metabolism of which accounts for the excess methane. The total concentration of all types of microbes we measured with direct counts of Syto-23-stained cells tracks the excess of methanogens that we identified by their F420 autofluorescence and provides independent evidence for anomalous layers. The metabolic rate we estimated for microbes at those depths is consistent with the Arrhenius relation for rates found earlier for microbes imprisoned in rock, sediment, and ice. It is roughly the same as the rate of spontaneous macromolecular damage inferred from laboratory data, suggesting that microbes imprisoned in ice expend metabolic energy mainly to repair damage to DNA and amino acids rather than to grow. Equating the loss rate of methane recently discovered in the Martian atmosphere to the production rate by possible methanogens, we estimate that a possible Martian habitat would be at a temperature of approximately 0 degrees C and that the concentration, if uniformly distributed in a 10-m-thick layer, would be approximately 1 cell per ml.
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Affiliation(s)
- H C Tung
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720, USA
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32
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Richardson MI, Mischna MA. Long-term evolution of transient liquid water on Mars. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004je002367] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Mark I. Richardson
- Division of Geological and Planetary Sciences; California Institute of Technology; Pasadena California USA
| | - Michael A. Mischna
- Jet Propulsion Laboratory; California Institute of Technology; Pasadena California USA
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33
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Hanna JC. Hydrological modeling of the Martian crust with application to the pressurization of aquifers. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004je002330] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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34
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Martínez-Alonso S. A volcanic interpretation of Gusev Crater surface materials from thermophysical, spectral, and morphological evidence. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004je002327] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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35
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Heldmann JL. Formation of Martian gullies by the action of liquid water flowing under current Martian environmental conditions. ACTA ACUST UNITED AC 2005. [DOI: 10.1029/2004je002261] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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36
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Reiss D. Absolute dune ages and implications for the time of formation of gullies in Nirgal Vallis, Mars. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2004je002251] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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37
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Christensen PR. Formation of recent martian gullies through melting of extensive water-rich snow deposits. Nature 2003; 422:45-8. [PMID: 12594459 DOI: 10.1038/nature01436] [Citation(s) in RCA: 260] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2002] [Accepted: 01/14/2003] [Indexed: 11/08/2022]
Abstract
The observation of gullies on Mars indicates the presence of liquid water near the surface in recent times, which is difficult to reconcile with the current cold climate. Gullies have been proposed to form through surface runoff from subsurface aquifers or through melting of near-surface ice under warmer conditions. But these gullies are observed to occur preferentially in cold mid-latitudes, where the presence of liquid water is less likely, and on isolated surfaces where groundwater seepage would not be expected, making both potential explanations unsatisfactory. Here I show that gullies can form by the melting of water-rich snow that has been transported from the poles to mid-latitudes during periods of high obliquity within the past 10(5) to 10(6) years (refs 5, 6). Melting within this snow can generate sufficient water to erode gullies in about 5,000 years. My proposed model for gully formation is consistent with the age and location of the gullies, and it explains the occurrence of liquid water in the cold mid-latitudes as well as on isolated surfaces. Remnants of the snowpacks are still present on mid-latitude, pole-facing slopes, and the recent or current occurrence of liquid water within them provides a potential abode for life.
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Affiliation(s)
- Philip R Christensen
- Department of Geological Sciences, Campus Box 876305, Arizona State University, Tempe, Arizona 85287-6305, USA.
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38
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Jakosky BM, Nealson KH, Bakermans C, Ley RE, Mellon MT. Subfreezing activity of microorganisms and the potential habitability of Mars' polar regions. ASTROBIOLOGY 2003; 3:343-350. [PMID: 14577883 DOI: 10.1089/153110703769016433] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The availability of water-ice at the surface in the Mars polar cap and within the top meter of the high-latitude regolith raises the question of whether liquid water can exist there under some circumstances and possibly support the existence of biota. We examine the minimum temperatures at which liquid water can exist at ice grain-dust grain and ice grain-ice grain contacts, the minimum subfreezing temperatures at which terrestrial organisms can grow or multiply, and the maximum temperatures that can occur in martian high-latitude and polar regions, to see if there is overlap. Liquid water can exist at grain contacts above about -20 degrees C. Measurements of growth in organisms isolated from Siberian permafrost indicate growth at -10 degrees C and metabolism at -20 degrees C. Mars polar and high-latitude temperatures rise above -20 degrees C at obliquities greater than ~40 degrees, and under some conditions rise above 0 degrees C. Thus, the environment in the Mars polar regions has overlapped habitable conditions within relatively recent epochs, and Mars appears to be on the edge of being habitable at present. The easy accessibility of the polar surface layer relative to the deep subsurface make these viable locations to search for evidence of life.
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Affiliation(s)
- Bruce M Jakosky
- Laboratory for Atmospheric and Space Physics, Department of Geological Sciences, University of Colorado, Boulder, CO 80303, USA.
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39
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40
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Milliken RE. Viscous flow features on the surface of Mars: Observations from high-resolution Mars Orbiter Camera (MOC) images. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002je002005] [Citation(s) in RCA: 219] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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41
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42
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Treiman AH. Geologic settings of Martian gullies: Implications for their origins. ACTA ACUST UNITED AC 2003. [DOI: 10.1029/2002je001900] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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43
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44
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45
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Stewart ST. Surface runoff features on Mars: Testing the carbon dioxide formation hypothesis. ACTA ACUST UNITED AC 2002. [DOI: 10.1029/2000je001465] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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46
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Jakosky BM, Mellon MT. High-resolution thermal inertia mapping of Mars: Sites of exobiological interest. ACTA ACUST UNITED AC 2001. [DOI: 10.1029/2000je001311] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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47
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Abstract
There is substantial evidence that the martian volatile inventory and climate have changed markedly throughout the planet's history. Clues come from areas as disparate as the history and properties of the deep interior, the composition of the crust and regolith, the morphology of the surface, composition of the present-day atmosphere, and the nature of the interactions between the upper atmosphere and the solar wind. We piece together the relevant observations into a coherent view of the evolution of the martian climate, focusing in particular on the observations that provide the strongest constraints.
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Affiliation(s)
- B M Jakosky
- Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, Colorado 80309-0392, USA.
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48
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Wynn-Williams DD, Cabrol NA, Grin EA, Haberle RM, Stoker CR. Brines in seepage channels as eluants for subsurface relict biomolecules on Mars? ASTROBIOLOGY 2001; 1:165-184. [PMID: 12467120 DOI: 10.1089/153110701753198936] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Water, vital for life, not only maintains the integrity of structural and metabolic biomolecules, it also transports them in solution or colloidal suspension. Any flow of water through a dormant or fossilized microbial community elutes molecules that are potentially recognizable as biomarkers. We hypothesize that the surface seepage channels emanating from crater walls and cliffs in Mars Orbiter Camera images results from fluvial erosion of the regolith as low-temperature hypersaline brines. We propose that, if such flows passed through extensive subsurface catchments containing buried and fossilized remains of microbial communities from the wet Hesperian period of early Mars (approximately 3.5 Ga ago), they would have eluted and concentrated relict biomolecules and delivered them to the surface. Life-supporting low-temperature hypersaline brines in Antarctic desert habitats provide a terrestrial analog for such a scenario. As in the Antarctic, salts would likely have accumulated in water-filled depressions on Mars by seasonal influx and evaporation. Liquid water in the Antarctic cold desert analogs occurs at -80 degrees C in the interstices of shallow hypersaline soils and at -50 degrees C in salt-saturated ponds. Similarly, hypersaline brines on Mars could have freezing points depressed below -50 degrees C. The presence of hypersaline brines on Mars would have extended the amount of time during which life might have evolved. Phototrophic communities are especially important for the search for life because the distinctive structures and longevity of their pigments make excellent biomarkers. The surface seepage channels are therefore not only of geomorphological significance, but also provide potential repositories for biomolecules that could be accessed by landers.
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Affiliation(s)
- D D Wynn-Williams
- British Antarctic Survey, Natural Environment Research Council, Cambridge CB3 OET, U.K.
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