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Astrobiology

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https://www.readbyqxmd.com/read/29039682/on-the-habitability-of-desert-varnish-a-combined-study-by-micro-raman-spectroscopy-x-ray-diffraction-and-methylated-pyrolysis-gas-chromatography-mass-spectrometry
#1
C Malherbe, I B Hutchinson, R Ingley, A Boom, A S Carr, H Edwards, B Vertruyen, B Gilbert, G Eppe
In 2020, the ESA ExoMars and NASA Mars 2020 missions will be launched to Mars to search for evidence of past and present life. In preparation for these missions, terrestrial analog samples of rock formations on Mars are studied in detail in order to optimize the scientific information that the analytical instrumentation will return. Desert varnishes are thin mineral coatings found on rocks in arid and semi-arid environments on Earth that are recognized as analog samples. During the formation of desert varnishes (which takes many hundreds of years), organic matter is incorporated, and microorganisms may also play an active role in the formation process...
October 17, 2017: Astrobiology
https://www.readbyqxmd.com/read/29023147/nitrogen-oxides-in-early-earth-s-atmosphere-as-electron-acceptors-for-life-s-emergence
#2
Michael L Wong, Benjamin D Charnay, Peter Gao, Yuk L Yung, Michael J Russell
We quantify the amount of nitrogen oxides (NOx) produced through lightning and photochemical processes in the Hadean atmosphere to be available in the Hadean ocean for the emergence of life. Atmospherically generated nitrate (NO3(-)) and nitrite (NO2(-)) are the most attractive high-potential electron acceptors for pulling and enabling crucial redox reactions of autotrophic metabolic pathways at submarine alkaline hydrothermal vents. The Hadean atmosphere, dominated by CO2 and N2, will produce nitric oxide (NO) when shocked by lightning...
October 12, 2017: Astrobiology
https://www.readbyqxmd.com/read/29019413/instrumentation-for-testing-whether-the-icy-moons-of-the-gas-and-ice-giants-are-inhabited
#3
Julian Chela-Flores
Evidence of life beyond Earth may be closer than we think, given that the forthcoming missions to the Jovian system will be equipped with instruments capable of probing Europa's icy surface for possible biosignatures, including chemical biomarkers, despite the strong radiation environment. Geochemical biomarkers may also exist beyond Europa on icy moons of the gas giants. Sulfur is proposed as a reliable geochemical biomarker for approved and forthcoming missions to the outer solar system. Key Words: JUICE mission-Clipper mission-Geochemical biomarkers-Europa-Moons of the ice giants-Geochemistry-Mass spectrometry...
October 11, 2017: Astrobiology
https://www.readbyqxmd.com/read/29016195/critical-assessment-of-analytical-techniques-in-the-search-for-biomarkers-on-mars-a-mummified-microbial-mat-from-antarctica-as-a-best-case-scenario
#4
Yolanda Blanco, Ignacio Gallardo-Carreño, Marta Ruiz-Bermejo, Fernando Puente-Sánchez, Erika Cavalcante-Silva, Antonio Quesada, Olga Prieto-Ballesteros, Víctor Parro
The search for biomarkers of present or past life is one of the major challenges for in situ planetary exploration. Multiple constraints limit the performance and sensitivity of remote in situ instrumentation. In addition, the structure, chemical, and mineralogical composition of the sample may complicate the analysis and interpretation of the results. The aim of this work is to highlight the main constraints, performance, and complementarity of several techniques that have already been implemented or are planned to be implemented on Mars for detection of organic and molecular biomarkers on a best-case sample scenario...
October 10, 2017: Astrobiology
https://www.readbyqxmd.com/read/29016193/the-possible-emergence-of-life-and-differentiation-of-a-shallow-biosphere-on-irradiated-icy-worlds-the-example-of-europa
#5
Michael J Russell, Alison E Murray, Kevin P Hand
Irradiated ice-covered ocean worlds with rocky mafic mantles may provide the conditions needed to drive the emergence and maintenance of life. Alkaline hydrothermal springs-relieving the geophysical, thermal, and chemical disequilibria between oceans and tidally stressed crusts-could generate inorganic barriers to the otherwise uncontrolled and kinetically disfavored oxidation of hydrothermal hydrogen and methane. Ionic gradients imposed across these inorganic barriers, comprising iron oxyhydroxides and sulfides, could drive the hydrogenation of carbon dioxide and the oxidation of methane through thermodynamically favorable metabolic pathways leading to early life-forms...
October 10, 2017: Astrobiology
https://www.readbyqxmd.com/read/28949766/methane-fuel-or-exhaust-at-the-emergence-of-life
#6
Michael J Russell, Wolfgang Nitschke
As many of the methanogens first encountered at hydrothermal vents were thermophilic to hyperthermophilic and comprised one of the lower roots of the evolutionary tree, it has been assumed that methanogenesis was one of the earliest, if not the earliest, pathway to life. It being well known that hydrothermal springs associated with serpentinization also bore abiotic methane, it had been further assumed that emergent biochemistry merely adopted and quickened this supposed serpentinization reaction. Yet, recent hydrothermal experiments simulating serpentinization have failed to generate methane so far, thus casting doubt on this assumption...
September 26, 2017: Astrobiology
https://www.readbyqxmd.com/read/28926282/bacterial-and-archaeal-lipids-recovered-from-subsurface-evaporites-of-dalangtan-playa-on-the-tibetan-plateau-and-their-astrobiological-implications
#7
Ziye Cheng, Long Xiao, Hongmei Wang, Huan Yang, Jingjing Li, Ting Huang, Yi Xu, Nina Ma
Qaidam Basin (Tibetan Plateau) is considered an applicable analogue to Mars with regard to sustained extreme aridity and abundant evaporites. To investigate the possibility of the preservation of microbial lipids under these Mars analog conditions, we conducted a mineralogical and organic geochemistry study on samples collected from two Quaternary sections in Dalangtan Playa, northwestern Qaidam Basin, which will enhance our understanding of the potential preservation of molecular biomarkers on Mars. Two sedimentary units were identified along two profiles: one salt unit characterized by a predominance of gypsum and halite, and one detrital unit with a decrease of gypsum and halite and enrichment in siliciclastic minerals...
September 19, 2017: Astrobiology
https://www.readbyqxmd.com/read/28910143/the-lost-city-hydrothermal-field-a-spectroscopic-and-astrobiological-analogue-for-nili-fossae-mars
#8
Elena S Amador, Joshua L Bandfield, William J Brazelton, Deborah Kelley
Low-temperature serpentinization is a critical process with respect to Earth's habitability and the Solar System. Exothermic serpentinization reactions commonly produce hydrogen as a direct by-product and typically produce short-chained organic compounds indirectly. Here, we present the spectral and mineralogical variability in rocks from the serpentine-driven Lost City Hydrothermal Field on Earth and the olivine-rich region of Nili Fossae on Mars. Near- and thermal-infrared spectral measurements were made from a suite of Lost City rocks at wavelengths similar to those for instruments collecting measurements of the martian surface...
September 14, 2017: Astrobiology
https://www.readbyqxmd.com/read/28910135/imaging-of-vanadium-in-microfossils-a-new-potential-biosignature
#9
Craig P Marshall, Alison Olcott Marshall, Jade B Aitken, Barry Lai, Stefan Vogt, Pierre Breuer, Philippe Steemans, Peter A Lay
The inability to unambiguously distinguish the biogenicity of microfossil-like structures in the ancient rock record is a fundamental predicament facing Archean paleobiologists and astrobiologists. Therefore, novel methods for discriminating biological from nonbiological chemistries of microfossil-like structures are of the utmost importance in the search for evidence of early life on Earth. This, too, is important for the search for life on Mars by in situ analyses via rovers or sample return missions for future analysis here on Earth...
September 14, 2017: Astrobiology
https://www.readbyqxmd.com/read/28771029/methane-seepage-on-mars-where-to-look-and-why
#10
Dorothy Z Oehler, Giuseppe Etiope
Methane on Mars is a topic of special interest because of its potential association with microbial life. The variable detections of methane by the Curiosity rover, orbiters, and terrestrial telescopes, coupled with methane's short lifetime in the martian atmosphere, may imply an active gas source in the planet's subsurface, with migration and surface emission processes similar to those known on Earth as "gas seepage." Here, we review the variety of subsurface processes that could result in methane seepage on Mars...
August 3, 2017: Astrobiology
https://www.readbyqxmd.com/read/29048225/protecting-our-investment-in-the-exploration-and-utilization-of-space
#11
Gerhard Kminek, Lennard A Fisk
No abstract text is available yet for this article.
October 2017: Astrobiology
https://www.readbyqxmd.com/read/29048224/the-power-of-self-skepticism-in-astrobiology
#12
Shawn D Domagal-Goldman
No abstract text is available yet for this article.
October 2017: Astrobiology
https://www.readbyqxmd.com/read/29048223/laboratory-investigations-on-the-survival-of-bacillus-subtilis-spores-in-deliquescent-salt-mars-analog-environments
#13
Danielle L Nuding, Raina V Gough, Kasthuri J Venkateswaran, James A Spry, Margaret A Tolbert
Observed features such as recurring slope lineae suggest that liquid water may exist on the surface and near-subsurface of Mars today. The presence of this liquid water, likely in the form of a brine, has important implications for the present-day water cycle, habitability, and planetary protection policies. It is possible that this water is formed, at least partially, by deliquescence of salts, a process during which hygroscopic salts absorb water vapor from the atmosphere and form a saturated liquid brine...
October 2017: Astrobiology
https://www.readbyqxmd.com/read/29048222/correlations-between-life-detection-techniques-and-implications-for-sampling-site-selection-in-planetary-analog-missions
#14
Diana M Gentry, Elena S Amador, Morgan L Cable, Nosheen Chaudry, Thomas Cullen, Malene B Jacobsen, Gayathri Murukesan, Edward W Schwieterman, Adam H Stevens, Amanda Stockton, George Tan, Chang Yin, David C Cullen, Wolf Geppert
We conducted an analog sampling expedition under simulated mission constraints to areas dominated by basaltic tephra of the Eldfell and Fimmvörðuháls lava fields (Iceland). Sites were selected to be "homogeneous" at a coarse remote sensing resolution (10-100 m) in apparent color, morphology, moisture, and grain size, with best-effort realism in numbers of locations and replicates. Three different biomarker assays (counting of nucleic-acid-stained cells via fluorescent microscopy, a luciferin/luciferase assay for adenosine triphosphate, and quantitative polymerase chain reaction (qPCR) to detect DNA associated with bacteria, archaea, and fungi) were characterized at four nested spatial scales (1 m, 10 m, 100 m, and >1 km) by using five common metrics for sample site representativeness (sample mean variance, group F tests, pairwise t tests, and the distribution-free rank sum H and u tests)...
October 2017: Astrobiology
https://www.readbyqxmd.com/read/28920443/four-fallacies-and-an-oversight-searching-for-martian-life
#15
J D Rummel, C A Conley
While it is anticipated that future human missions to Mars will increase the amount of biological and organic contamination that might be distributed on that planet, robotic missions continue to grow in capability and complexity, requiring precautions to be taken now to protect Mars, and particularly areas of Mars that might be Special Regions. Such precautionary cleanliness requirements for spacecraft have evolved over the course of the space age, as we have learned more about planetary environments, and are the subject of regular deliberations and decisions sponsored by the Committee on Space Research (COSPAR)...
October 2017: Astrobiology
https://www.readbyqxmd.com/read/28885042/searching-for-life-on-mars-before-it-is-too-late
#16
Alberto G Fairén, Victor Parro, Dirk Schulze-Makuch, Lyle Whyte
Decades of robotic exploration have confirmed that in the distant past, Mars was warmer and wetter and its surface was habitable. However, none of the spacecraft missions to Mars have included among their scientific objectives the exploration of Special Regions, those places on the planet that could be inhabited by extant martian life or where terrestrial microorganisms might replicate. A major reason for this is because of Planetary Protection constraints, which are implemented to protect Mars from terrestrial biological contamination...
October 2017: Astrobiology
https://www.readbyqxmd.com/read/28443722/reflections-on-o2-as-a-biosignature-in-exoplanetary-atmospheres
#17
Victoria S Meadows
Oxygenic photosynthesis is Earth's dominant metabolism, having evolved to harvest the largest expected energy source at the surface of most terrestrial habitable zone planets. Using CO2 and H2O-molecules that are expected to be abundant and widespread on habitable terrestrial planets-oxygenic photosynthesis is plausible as a significant planetary process with a global impact. Photosynthetic O2 has long been considered particularly robust as a sign of life on a habitable exoplanet, due to the lack of known "false positives"-geological or photochemical processes that could also produce large quantities of stable O2...
October 2017: Astrobiology
https://www.readbyqxmd.com/read/28915088/abiotic-and-biotic-formation-of-amino-acids-in-the-enceladus-ocean
#18
Elliot L Steel, Alfonso Davila, Christopher P McKay
The active plume at Enceladus' south pole makes the indirect sampling of its global ocean possible. The partially resolved chemistry of the plume, which points to conditions that are seemingly compatible with life, has made orbital sampling missions a priority. We present a conceptual model of energy flux, hydrothermal H2 production, and both abiotic and biotic production of amino acids. Based on the energy flux observed at the south pole and the inferred internal hydrothermal activity, we estimate an H2 production of 0...
September 2017: Astrobiology
https://www.readbyqxmd.com/read/28915087/feasibility-of-detecting-bioorganic-compounds-in-enceladus-plumes-with-the-enceladus-organic-analyzer
#19
Richard A Mathies, Md Enayet Razu, Jungkyu Kim, Amanda M Stockton, Paul Turin, Anna Butterworth
Enceladus presents an excellent opportunity to detect organic molecules that are relevant for habitability as well as bioorganic molecules that provide evidence for extraterrestrial life because Enceladus' plume is composed of material from the subsurface ocean that has a high habitability potential and significant organic content. A primary challenge is to send instruments to Enceladus that can efficiently sample organic molecules in the plume and analyze for the most relevant molecules with the necessary detection limits...
September 2017: Astrobiology
https://www.readbyqxmd.com/read/28872900/enceladus-plume-structure-and-time-variability-comparison-of-cassini-observations
#20
Ben D Teolis, Mark E Perry, Candice J Hansen, J Hunter Waite, Carolyn C Porco, John R Spencer, Carly J A Howett
During three low-altitude (99, 66, 66 km) flybys through the Enceladus plume in 2010 and 2011, Cassini's ion neutral mass spectrometer (INMS) made its first high spatial resolution measurements of the plume's gas density and distribution, detecting in situ the individual gas jets within the broad plume. Since those flybys, more detailed Imaging Science Subsystem (ISS) imaging observations of the plume's icy component have been reported, which constrain the locations and orientations of the numerous gas/grain jets...
September 2017: Astrobiology
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