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Astrobiology

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https://www.readbyqxmd.com/read/29461869/volcanogenic-pseudo-fossils-from-the-%C3%A2-3-48-ga-dresser-formation-pilbara-western-australia
#1
David Wacey, Nora Noffke, Martin Saunders, Paul Guagliardo, David M Pyle
The ∼3.48 billion-year-old Dresser Formation, Pilbara Craton, Western Australia, is a key geological unit for the study of Earth's earliest life and the habitats it occupied. Here, we describe a new suite of spheroidal to lenticular microstructures that morphologically resemble some previously reported Archean microfossils. Correlative microscopy shows that these objects have a size distribution, wall ultrastructure, and chemistry that are incompatible with a microfossil origin and instead are interpreted as pyritized and silicified fragments of vesicular volcanic glass...
February 20, 2018: Astrobiology
https://www.readbyqxmd.com/read/29443541/a-method-for-choosing-the-best-samples-for-mars-sample-return
#2
Peter R Gordon, Mark A Sephton
Success of a future Mars Sample Return mission will depend on the correct choice of samples. Pyrolysis-FTIR can be employed as a triage instrument for Mars Sample Return. The technique can thermally dissociate minerals and organic matter for detection. Identification of certain mineral types can determine the habitability of the depositional environment, past or present, while detection of organic matter may suggest past or present habitation. In Mars' history, the Theiikian era represents an attractive target for life search missions and the acquisition of samples...
February 14, 2018: Astrobiology
https://www.readbyqxmd.com/read/29431479/the-habitability-of-proxima-centauri-b-environmental-states-and-observational-discriminants
#3
Victoria S Meadows, Giada N Arney, Edward W Schwieterman, Jacob Lustig-Yaeger, Andrew P Lincowski, Tyler Robinson, Shawn D Domagal-Goldman, Russell Deitrick, Rory K Barnes, David P Fleming, Rodrigo Luger, Peter E Driscoll, Thomas R Quinn, David Crisp
Proxima Centauri b provides an unprecedented opportunity to understand the evolution and nature of terrestrial planets orbiting M dwarfs. Although Proxima Cen b orbits within its star's habitable zone, multiple plausible evolutionary paths could have generated different environments that may or may not be habitable. Here, we use 1-D coupled climate-photochemical models to generate self-consistent atmospheres for several evolutionary scenarios, including high-O2, high-CO2, and more Earth-like atmospheres, with both oxic and anoxic compositions...
February 12, 2018: Astrobiology
https://www.readbyqxmd.com/read/29424566/evaluation-of-the-tindouf-basin-region-in-southern-morocco-as-an-analog-site-for-soil-geochemistry-on-noachian-mars
#4
Elizabeth A Oberlin, Mark W Claire, Samuel P Kounaves
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)...
February 9, 2018: Astrobiology
https://www.readbyqxmd.com/read/29394085/2017-acknowledgment-of-reviewers
#5
(no author information available yet)
No abstract text is available yet for this article.
February 2, 2018: Astrobiology
https://www.readbyqxmd.com/read/29381372/thinking-differently-about-risk
#6
Andrew D Maynard
No abstract text is available yet for this article.
January 30, 2018: Astrobiology
https://www.readbyqxmd.com/read/29377716/the-uk-centre-for-astrobiology-a-virtual-astrobiology-centre-accomplishments-and-lessons-learned-2011-2016
#7
Charles S Cockell, Beth Biller, Casey Bryce, Claire Cousins, Susana Direito, Duncan Forgan, Mark Fox-Powell, Jesse Harrison, Hanna Landenmark, Sophie Nixon, Samuel J Payler, Ken Rice, Toby Samuels, Petra Schwendner, Adam Stevens, Natasha Nicholson, Jennifer Wadsworth
The UK Centre for Astrobiology (UKCA) was set up in 2011 as a virtual center to contribute to astrobiology research, education, and outreach. After 5 years, we describe this center and its work in each of these areas. Its research has focused on studying life in extreme environments, the limits of life on Earth, and implications for habitability elsewhere. Among its research infrastructure projects, UKCA has assembled an underground astrobiology laboratory that has hosted a deep subsurface planetary analog program, and it has developed new flow-through systems to study extraterrestrial aqueous environments...
January 29, 2018: Astrobiology
https://www.readbyqxmd.com/read/29364704/the-effect-of-varying-atmospheric-pressure-upon-habitability-and-biosignatures-of-earth-like-planets
#8
Engin Keles, John Lee Grenfell, Mareike Godolt, Barbara Stracke, Heike Rauer
Understanding the possible climatic conditions on rocky extrasolar planets, and thereby their potential habitability, is one of the major subjects of exoplanet research. Determining how the climate, as well as potential atmospheric biosignatures, changes under different conditions is a key aspect when studying Earth-like exoplanets. One important property is the atmospheric mass, hence pressure and its influence on the climatic conditions. Therefore, the aim of the present study is to understand the influence of atmospheric mass on climate, hence habitability, and the spectral appearance of planets with Earth-like, that is, N2-O2 dominated, atmospheres orbiting the Sun at 1 AU...
January 24, 2018: Astrobiology
https://www.readbyqxmd.com/read/29359967/is-searching-for-martian-life-a-priority-for-the-mars-community
#9
Alberto G Fairén, Victor Parro, Dirk Schulze-Makuch, Lyle Whyte
No abstract text is available yet for this article.
January 23, 2018: Astrobiology
https://www.readbyqxmd.com/read/29319335/astrovirology-viruses-at-large-in-the-universe
#10
Aaron J Berliner, Tomohiro Mochizuki, Kenneth M Stedman
Viruses are the most abundant biological entities on modern Earth. They are highly diverse both in structure and genomic sequence, play critical roles in evolution, strongly influence terran biogeochemistry, and are believed to have played important roles in the origin and evolution of life. However, there is yet very little focus on viruses in astrobiology. Viruses arguably have coexisted with cellular life-forms since the earliest stages of life, may have been directly involved therein, and have profoundly influenced cellular evolution...
January 10, 2018: Astrobiology
https://www.readbyqxmd.com/read/29314901/secondary-electrons-as-an-energy-source-for-life
#11
Kamil B Stelmach, Marc Neveu, Trista J Vick-Majors, Rebecca L Mickol, Luoth Chou, Kevin D Webster, Matt Tilley, Federica Zacchei, Cristina Escudero, Claudio L Flores Martinez, Amanda Labrado, Enrique J G Fernández
Life on Earth is found in a wide range of environments as long as the basic requirements of a liquid solvent, a nutrient source, and free energy are met. Previous hypotheses have speculated how extraterrestrial microbial life may function, among them that particle radiation might power living cells indirectly through radiolytic products. On Earth, so-called electrophilic organisms can harness electron flow from an extracellular cathode to build biomolecules. Here, we describe two hypothetical mechanisms, termed "direct electrophy" and "indirect electrophy" or "fluorosynthesis," by which organisms could harness extracellular free electrons to synthesize organic matter, thus expanding the ensemble of potential habitats in which extraterrestrial organisms might be found in the Solar System and beyond...
January 9, 2018: Astrobiology
https://www.readbyqxmd.com/read/29298093/the-search-for-hesperian-organic-matter-on-mars-pyrolysis-studies-of-sediments-rich-in-sulfur-and-iron
#12
James M T Lewis, Jens Najorka, Jonathan S Watson, Mark A Sephton
Jarosite on Mars is of significant geological and astrobiological interest, as it forms in acidic aqueous conditions that are potentially habitable for acidophilic organisms. Jarosite can provide environmental context and may host organic matter. The most common extraction technique used to search for organic compounds on the surface of Mars is pyrolysis. However, thermal decomposition of jarosite releases oxygen into pyrolysis ovens, which degrades organic signals. Jarosite has a close association with the iron oxyhydroxide goethite in many depositional/diagenetic environments...
January 3, 2018: Astrobiology
https://www.readbyqxmd.com/read/29297697/the-impact-of-the-temporal-distribution-of-communicating-civilizations-on-their-detectability
#13
Amedeo Balbi
We used a statistical model to investigate the detectability (defined by the requirement that causal contact has been initiated with us) of communicating civilizations within a volume of the Universe surrounding our location. If the civilizations are located in our galaxy, the detectability requirement imposes a strict constraint on their epoch of appearance and their communicating life span. This, in turn, implies that our ability to gather empirical evidence of the fraction of civilizations within range of detection strongly depends on the specific features of their temporal distribution...
January 3, 2018: Astrobiology
https://www.readbyqxmd.com/read/29283671/photobiological-effects-at-earth-s-surface-following-a-50%C3%A2-pc-supernova
#14
Brian C Thomas
We investigated the potential biological impacts at Earth's surface of stratospheric O3 depletion caused by nearby supernovae known to have occurred about 2.5 and 8 million years ago at about 50 pc distance. New and previously published atmospheric chemistry modeling results were combined with radiative transfer modeling to determine changes in surface-level solar irradiance and biological responses. We find that UVB irradiance is increased by a factor of 1.1 to 2.8, with large variation in latitude, and seasonally at high-latitude regions...
December 28, 2017: Astrobiology
https://www.readbyqxmd.com/read/29265883/electron-transfer-strategies-regulate-carbonate-mineral-and-micropore-formation
#15
Zhirui Zeng, Michael M Tice
Some microbial carbonates are robust biosignatures due to their distinct morphologies and compositions. However, whether carbonates induced by microbial iron reduction have such features is unknown. Iron-reducing bacteria use various strategies to transfer electrons to iron oxide minerals (e.g., membrane-bound enzymes, soluble electron shuttles, nanowires, as well as different mechanisms for moving over or attaching to mineral surfaces). This diversity has the potential to create mineral biosignatures through manipulating the microenvironments in which carbonate precipitation occurs...
December 21, 2017: Astrobiology
https://www.readbyqxmd.com/read/29227145/transport-induced-spatial-patterns-of-sulfur-isotopes-%C3%AE-34s-as-biosignatures
#16
Muammar Mansor, Khadouja Harouaka, Matthew S Gonzales, Jennifer L Macalady, Matthew S Fantle
Cave minerals deposited in the presence of microbes may host geochemical biosignatures that can be utilized to detect subsurface life on Earth, Mars, or other habitable worlds. The sulfur isotopic composition of gypsum (CaSO4·2H2O) formed in the presence of sulfur-oxidizing microbes in the Frasassi cave system, Italy, was evaluated as a biosignature. Sulfur isotopic compositions (δ34SV-CDT) of gypsum sampled from cave rooms with sulfidic air varied from -11 to -24‰, with minor deposits of elemental sulfur having δ34S values between -17 and -19‰...
December 11, 2017: Astrobiology
https://www.readbyqxmd.com/read/29189043/an-antarctic-extreme-halophile-and-its-polyextremophilic-enzyme-effects-of-perchlorate-salts
#17
Victoria J Laye, Shiladitya DasSarma
Effects of perchlorate salts prevalent on the surface of Mars are of significant interest to astrobiology from the perspective of potential life on the Red Planet. Halorubrum lacusprofundi, a cold-adapted halophilic Antarctic archaeon, was able to grow anaerobically on 0.04 M concentration of perchlorate. With increasing concentrations of perchlorate, growth was inhibited, with half-maximal growth rate in ca. 0.3 M NaClO4 and 0.1 M Mg(ClO4)2 under aerobic conditions. Magnesium ions were also inhibitory for growth, but at considerably higher concentrations, with half-maximal growth rate above 1 M...
November 30, 2017: Astrobiology
https://www.readbyqxmd.com/read/29189040/organic-haze-as-a-biosignature-in-anoxic-earth-like-atmospheres
#18
Giada Arney, Shawn D Domagal-Goldman, Victoria S Meadows
Early Earth may have hosted a biologically mediated global organic haze during the Archean eon (3.8-2.5 billion years ago). This haze would have significantly impacted multiple aspects of our planet, including its potential for habitability and its spectral appearance. Here, we model worlds with Archean-like levels of carbon dioxide orbiting the ancient Sun and an M4V dwarf (GJ 876) and show that organic haze formation requires methane fluxes consistent with estimated Earth-like biological production rates...
November 30, 2017: Astrobiology
https://www.readbyqxmd.com/read/29451824/inadvertently-finding-earth-contamination-on-mars-should-not-be-a-priority-for-anyone
#19
John D Rummel, Catharine A Conley
No abstract text is available yet for this article.
February 2018: Astrobiology
https://www.readbyqxmd.com/read/29345987/habitable-worlds-delivering-on-the-promises-of-online-education
#20
Lev B Horodyskyj, Chris Mead, Zack Belinson, Sanlyn Buxner, Steven Semken, Ariel D Anbar
Critical thinking and scientific reasoning are central to higher education in the United States, but many courses (in-person and online) teach students information about science much more than they teach the actual process of science and its associated knowledge and skills. In the online arena specifically, the tools available for course construction exacerbate this problem by making it difficult to build the types of active learning activities that research shows to be the most effective. Here, we present a report on Habitable Worlds, offered by Arizona State University for 12 semesters over the past 6 years...
January 2018: Astrobiology
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