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Gilbert V Levin, Patricia Ann Straat
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July 16, 2018: Astrobiology
Manasvi Lingam, Abraham Loeb
As evident from the nearby examples of Proxima Centauri and TRAPPIST-1, Earth-sized planets in the habitable zone of low-mass stars are common. Here, we focus on such planetary systems and argue that their (oceanic) tides could be more prominent due to stronger tidal forces. We identify the conditions under which tides may exert a significant positive influence on biotic processes including abiogenesis, biological rhythms, nutrient upwelling, and stimulating photosynthesis. We conclude our analysis with the identification of large-scale algal blooms as potential temporal biosignatures in reflectance light curves that can arise indirectly as a consequence of strong tidal forces...
July 16, 2018: Astrobiology
Jennifer Ronholm, Jacqueline Goordial, Haley M Sapers, Matthew R M Izawa, Daniel M Applin, Alexandra Pontefract, Christopher R Omelon, Guillaume Lamarche-Gagnon, Edward A Cloutis, Lyle G Whyte
The microbial ecology and activity of serpentine deposits and associated hydrated minerals are largely unknown. Previous research has largely focused on microbial communities in active serpentinizing systems, whereas relatively little research has demonstrated the ability of serpentine deposits to host microbial communities after the cessation of serpentinization. Given the potential role of serpentinization reactions fueling primitive microbial metabolisms on early Earth and the identification of serpentine deposits on Mars, knowledge of these geobiological relationships and potential for serpentine to host extant microbial communities and preserve biosignatures is increasingly important for planetary exploration seeking signs of life...
July 10, 2018: Astrobiology
Marc Neveu, Lindsay E Hays, Mary A Voytek, Michael H New, Mitchell D Schulte
We describe the history and features of the Ladder of Life Detection, a tool intended to guide the design of investigations to detect microbial life within the practical constraints of robotic space missions. To build the Ladder, we have drawn from lessons learned from previous attempts at detecting life and derived criteria for a measurement (or suite of measurements) to constitute convincing evidence for indigenous life. We summarize features of life as we know it, how specific they are to life, and how they can be measured, and sort these features in a general sense based on their likelihood of indicating life...
June 4, 2018: Astrobiology
Fanjing Kong, Mianping Zheng, Bin Hu, Alian Wang, Nina Ma, Pablo Sobron
Since 2008, we have been studying a saline lake, Dalangtan (DLT) Playa, and its surroundings in a hyperarid region of the Qaidam Basin on the Tibetan Plateau as a potential Mars analog site. We describe the evolution of saline deposits in the Qaidam Basin (including DLT), based on investigative findings accumulated over the course of 60 years of geological surveys. In addition, we report regional meteorological patterns recorded for the past 32 years along with meteorological station recorded data at DLT since 2012...
May 24, 2018: Astrobiology
Tiago Alves Jorge de Souza, Tiago Campos Pereira
One of the most important laboratory animal species is the nematode Caenorhabditis elegans, which has been used in a range of research fields such as neurobiology, body development, and molecular biology. The scientific progress obtained by employing C. elegans as a model in these areas has encouraged its use in new fields. One of the new potential applications concerns the biological responses to hyperacceleration stress (g-force), but only a few studies have evaluated the response of multicellular organisms to extreme hypergravity conditions at the order of magnitude 105  x g, which is the theorized force experienced by rocks ejected from Mars (or similar planets)...
May 10, 2018: Astrobiology
Edward W Schwieterman, Nancy Y Kiang, Mary N Parenteau, Chester E Harman, Shiladitya DasSarma, Theresa M Fisher, Giada N Arney, Hilairy E Hartnett, Christopher T Reinhard, Stephanie L Olson, Victoria S Meadows, Charles S Cockell, Sara I Walker, John Lee Grenfell, Siddharth Hegde, Sarah Rugheimer, Renyu Hu, Timothy W Lyons
In the coming years and decades, advanced space- and ground-based observatories will allow an unprecedented opportunity to probe the atmospheres and surfaces of potentially habitable exoplanets for signatures of life. Life on Earth, through its gaseous products and reflectance and scattering properties, has left its fingerprint on the spectrum of our planet. Aided by the universality of the laws of physics and chemistry, we turn to Earth's biosphere, both in the present and through geologic time, for analog signatures that will aid in the search for life elsewhere...
May 4, 2018: Astrobiology
Brian M Hynek, Karyn L Rogers, Monique Antunovich, Geoffroy Avard, Guillermo E Alvarado
The Poás volcano in Costa Rica has been studied as a Mars geochemical analog environment, since both the style of hydrothermal alteration present and the alteration mineralogy are consistent with Mars' relict hydrothermal systems. The site hosts an active volcano, with high-temperature fumaroles (up to 980°C) and an ultra-acidic lake. This lake, Laguna Caliente, is one of the most dynamic environments on Earth, with frequent phreatic eruptions, temperatures ranging from near-ambient to almost boiling, a pH range of -1 to 1...
April 24, 2018: Astrobiology
Sara I Walker, William Bains, Leroy Cronin, Shiladitya DasSarma, Sebastian Danielache, Shawn Domagal-Goldman, Betul Kacar, Nancy Y Kiang, Adrian Lenardic, Christopher T Reinhard, William Moore, Edward W Schwieterman, Evgenya L Shkolnik, Harrison B Smith
We introduce a Bayesian method for guiding future directions for detection of life on exoplanets. We describe empirical and theoretical work necessary to place constraints on the relevant likelihoods, including those emerging from better understanding stellar environment, planetary climate and geophysics, geochemical cycling, the universalities of physics and chemistry, the contingencies of evolutionary history, the properties of life as an emergent complex system, and the mechanisms driving the emergence of life...
June 2018: Astrobiology
Yuka Fujii, Daniel Angerhausen, Russell Deitrick, Shawn Domagal-Goldman, John Lee Grenfell, Yasunori Hori, Stephen R Kane, Enric Pallé, Heike Rauer, Nicholas Siegler, Karl Stapelfeldt, Kevin B Stevenson
Exoplanet hunting efforts have revealed the prevalence of exotic worlds with diverse properties, including Earth-sized bodies, which has fueled our endeavor to search for life beyond the Solar System. Accumulating experiences in astrophysical, chemical, and climatological characterization of uninhabitable planets are paving the way to characterization of potentially habitable planets. In this paper, we review our possibilities and limitations in characterizing temperate terrestrial planets with future observational capabilities through the 2030s and beyond, as a basis of a broad range of discussions on how to advance "astrobiology" with exoplanets...
June 2018: Astrobiology
Victoria S Meadows, Christopher T Reinhard, Giada N Arney, Mary N Parenteau, Edward W Schwieterman, Shawn D Domagal-Goldman, Andrew P Lincowski, Karl R Stapelfeldt, Heike Rauer, Shiladitya DasSarma, Siddharth Hegde, Norio Narita, Russell Deitrick, Jacob Lustig-Yaeger, Timothy W Lyons, Nicholas Siegler, J Lee Grenfell
We describe how environmental context can help determine whether oxygen (O2 ) detected in extrasolar planetary observations is more likely to have a biological source. Here we provide an in-depth, interdisciplinary example of O2 biosignature identification and observation, which serves as the prototype for the development of a general framework for biosignature assessment. Photosynthetically generated O2 is a potentially strong biosignature, and at high abundance, it was originally thought to be an unambiguous indicator for life...
June 2018: Astrobiology
Nancy Y Kiang, Shawn Domagal-Goldman, Mary N Parenteau, David C Catling, Yuka Fujii, Victoria S Meadows, Edward W Schwieterman, Sara I Walker
The rapid rate of discoveries of exoplanets has expanded the scope of the science possible for the remote detection of life beyond Earth. The Exoplanet Biosignatures Workshop Without Walls (EBWWW) held in 2016 engaged the international scientific community across diverse scientific disciplines, to assess the state of the science and technology in the search for life on exoplanets, and to identify paths for progress. The workshop activities resulted in five major review papers, which provide (1) an encyclopedic review of known and proposed biosignatures and models used to ascertain them (Schwieterman et al...
June 2018: Astrobiology
A Frank, Jonathan Carroll-Nellenback, M Alberti, A Kleidon
We present a framework for studying generic behaviors possible in the interaction between a resource-harvesting technological civilization (an exo-civilization) and the planetary environment in which it evolves. Using methods from dynamical systems theory, we introduce and analyze a suite of simple equations modeling a population which consumes resources for the purpose of running a technological civilization and the feedback those resources drive on the state of the host planet. The feedbacks can drive the planet away from the initial state the civilization originated in and into domains that are detrimental to its sustainability...
May 2018: Astrobiology
Andrew J Rushby, Martin Johnson, Benjamin J W Mills, Andrew J Watson, Mark W Claire
The potential habitability of an exoplanet is traditionally assessed by determining whether its orbit falls within the circumstellar "habitable zone" of its star, defined as the distance at which water could be liquid on the surface of a planet (Kopparapu et al., 2013 ). Traditionally, these limits are determined by radiative-convective climate models, which are used to predict surface temperatures at user-specified levels of greenhouse gases. This approach ignores the vital question of the (bio)geochemical plausibility of the proposed chemical abundances...
May 2018: Astrobiology
Huan Cui, Kouki Kitajima, Michael J Spicuzza, John H Fournelle, Akizumi Ishida, Philip E Brown, John W Valley
Sedimentological observations from the Paleoproterozoic Huronian Supergroup are suggested to mark the rise in atmospheric oxygen at that time, which is commonly known as the Great Oxidation Event (GOE) and typically coupled with a transition from mass-independent fractionation (MIF) to mass-dependent fractionation (MDF) of sulfur isotopes. An early in situ study of S three-isotopes across the Huronian Supergroup by Papineau et al. ( 2007 ) identified a weak MIF-MDF transition. However, the interpretation and stratigraphic placement of this transition is ambiguous...
May 2018: Astrobiology
Catherine D Neish, Ralph D Lorenz, Elizabeth P Turtle, Jason W Barnes, Melissa G Trainer, Bryan Stiles, Randolph Kirk, Charles A Hibbitts, Michael J Malaska
Saturn's moon Titan has all the ingredients needed to produce "life as we know it." When exposed to liquid water, organic molecules analogous to those found on Titan produce a range of biomolecules such as amino acids. Titan thus provides a natural laboratory for studying the products of prebiotic chemistry. In this work, we examine the ideal locales to search for evidence of, or progression toward, life on Titan. We determine that the best sites to identify biological molecules are deposits of impact melt on the floors of large, fresh impact craters, specifically Sinlap, Selk, and Menrva craters...
May 2018: Astrobiology
Milan M Ćirković
Jared Diamond's argument against extraterrestrial intelligence from evolutionary contingency is subjected to critical scrutiny. As with the earlier arguments of George Gaylord Simpson, it contains critical loopholes that lead to its unraveling. From the point of view of the contemporary debates about biological evolution, perhaps the most contentious aspect of such arguments is their atemporal and gradualist usage of the space of all possible biological forms (morphospace). Such usage enables the translation of the adaptive value of a trait into the probability of its evolving...
May 2018: Astrobiology
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...
May 2018: Astrobiology
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...
May 2018: Astrobiology
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...
May 2018: Astrobiology
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