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Stanley G Love
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September 8, 2018: Astrobiology
Anthony D Del Genio, Michael J Way, David S Amundsen, Igor Aleinov, Maxwell Kelley, Nancy Y Kiang, Thomas L Clune
The nearby exoplanet Proxima Centauri b will be a prime future target for characterization, despite questions about its retention of water. Climate models with static oceans suggest that Proxima b could harbor a small dayside surface ocean despite its weak instellation. We present the first climate simulations of Proxima b with a dynamic ocean. We find that an ocean-covered Proxima b could have a much broader area of surface liquid water but at much colder temperatures than previously suggested, due to ocean heat transport and/or depression of the freezing point by salinity...
September 5, 2018: Astrobiology
Kunio Kawamura, Noriko Konagaya, Yoshimi Maruoka
In a previous study, we have showed that the elongation of an alanine oligopeptide [L-alanyl-L-alanyl-L-alanyl-L-alanine ((Ala)4 )] to higher oligopeptides is enhanced by calcite and dolomite at 275°C, using a mineral-mediated hydrothermal flow reactor system. However, a problem during the use of hydrothermal flow reactor system was that some of the minerals, such as clay, could not be tested due to their clogging in the reactor. In this article, we attempted to analyze the scope of enhancement for the formation of L-alanyl-L-alanyl-L-alanyl-L-alanyl-L-alanine ((Ala)5 ) and higher oligopeptides with different minerals including clay minerals for the elongation of alanine oligopeptide at 175°C...
August 30, 2018: Astrobiology
Alian Wang, Pablo Sobron, Fanjing Kong, Mianping Zheng, Yu-Yan Sara Zhao
Based on a field expedition to the Dalangtan (DLT) saline playa located in a hyperarid region (Qaidam Basin) on the Tibet Plateau and follow-up investigations, we report the mineralogy and geochemistry of the salt layers in two vertical stratigraphic cross sections in the DLT playa. Na-, Ca-, Mg-, KCaMg-sulfates; Na-, K-, KMg-chlorides; mixed (K, Mg)-chloride-sulfate; and chlorate and perchlorate were identified in the collected samples. This mineral assemblage represents the last-stage precipitation products from Na-K-Mg-Ca-Cl-SO4 brine and the oxychlorine formation from photochemistry reaction similar to other hyperarid regions on Earth...
August 28, 2018: Astrobiology
Courtney L Bartlett, Elisabeth M Hausrath, Christopher T Adcock, Shichun Huang, Zoe R Harrold, Arya Udry
Phosphate is an essential nutrient for life on Earth, present in adenosine triphosphate (ATP), deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and phospholipid membranes. Phosphorus does not have a significant volatile phase, and its release from minerals is therefore critical to its bioavailability. Organic ligands can enhance phosphate release from minerals relative to release in inorganic solutions, and phosphorus depletion in paleosols has consequently been used as a signature of the presence of ligands secreted by terrestrial organisms on early Earth...
August 22, 2018: Astrobiology
Tomonori Totani, Hidetoshi Omiya, Takahiro Sudoh, Masakazu A R Kobayashi, Masahiro Nagashima
The observed value Λobs of the cosmological constant Λ is extremely smaller than theoretical expectations, and the anthropic argument has been proposed as a solution to this problem because galaxies do not form when Λ ≫ Λobs . However, the contemporary galaxy formation theory predicts that stars form even with a high value of Λ/Λobs ∼ 50, which makes the anthropic argument less persuasive. Here we calculate the probability distribution of Λ using a model of cosmological galaxy formation, considering extinction of observers caused by radiation from nearby supernovae...
August 21, 2018: Astrobiology
Christos D Georgiou
The present study proposes to search our solar system (Mars, Enceladus, Europa) for patterns of organic molecules that are universally associated with biological functions and structures. The functions are primarily catalytic because life could only have originated within volume/space-constrained compartments containing chemical reactions catalyzed by certain polymers. The proposed molecular structures are specific groups in the side chains of amino acids with the highest catalytic propensities related to life on Earth, that is, those that most frequently participate as key catalytic groups in the active sites of enzymes such as imidazole, thiol, guanidinium, amide, and carboxyl...
August 21, 2018: Astrobiology
Svetlana Shkolyar, Jack D Farmer
Assessing biosignature preservation potential (BPP) in ancient habitable environments on Mars is a top NASA priority. We address this goal through the study of Miocene-Pliocene evaporites of the Verde Formation (central Arizona). We assessed the effects of diagenesis on BPP, integrating outcrop-scale observations with six lab analyses: thin-section petrography, X-ray diffraction, Raman spectroscopy, total organic carbon (TOC), electron probe microanalysis (EPMA), and visible to near-infrared (VNIR) reflectance spectroscopy...
August 20, 2018: Astrobiology
Roberto Barbieri, Barbara Cavalazzi
Small-scale terracing (microterracettes) is a surface geomorphic feature that recurs under a range of environmental settings, such as those existing in high to low temperature geothermal springs and evaporitic environments, through the single or combined action of physicochemical agents and microbiological processes. Such morphology can also be observed in a confined sector of the Sabkha Oum Dba, which is an inland sabkha of the Western Sahara (Morocco), where field and laboratory investigations revealed that they primarily depend on the accumulation of naviculoid diatoms...
August 10, 2018: Astrobiology
Pablo Sobron, Alian Wang, David P Mayer, Jennifer Bentz, Fanjing Kong, Mianping Zheng
We report the first multiscale, systematic field-based testing of correlations between orbital scale advanced spaceborne thermal emission and reflection radiometer visible near-infrared (VNIR)/shortwave infrared (SWIR) reflectance and thermal infrared relative emissivity and outcrop scale Raman spectroscopy, VNIR reflectance, X-ray diffraction (XRD), and laser-induced breakdown spectroscopy (LIBS) mineralogy and chemistry in a saline dry lakebed. This article is one of three reports describing the evolution of salt deposits, meteorological record, and surface and subsurface salt mineralogy in Dalangtan, Qaidam Basin, a hyperarid region of the Tibet Plateau, China, as potential environmental, mineralogical, and biogeochemical analogues to Mars...
August 10, 2018: Astrobiology
Matt A Tilley, Antígona Segura, Victoria Meadows, Suzanne Hawley, James Davenport
Understanding the impact of active M dwarf stars on the atmospheric equilibrium and surface conditions of a habitable zone Earth-like planet is key to assessing M dwarf planet habitability. Previous modeling of the impact of electromagnetic (EM) radiation and protons from a single large flare on an Earth-like atmosphere indicated that significant and long-term reductions in ozone were possible, but the atmosphere recovered. However, these stars more realistically exhibit frequent flaring with a distribution of different total energies and cadences...
August 2, 2018: Astrobiology
Yolanda Blanco, Graciela de Diego-Castilla, Daniel Viúdez-Moreiras, Erika Cavalcante-Silva, José Antonio Rodríguez-Manfredi, Alfonso F Davila, Christopher P McKay, Victor Parro
High-energy ionizing radiation in the form of solar energetic particles and galactic cosmic rays is pervasive on the surface of planetary bodies with thin atmospheres or in space facilities for humans, and it may seriously affect the chemistry and the structure of organic and biological material. We used fluorescent microarray immunoassays to assess how different doses of electron and gamma radiations affect the stability of target compounds such as biological polymers and small molecules (haptens) conjugated to large proteins...
August 2, 2018: Astrobiology
Claudia Pacelli, Laura Selbmann, Laura Zucconi, Claudia Coleine, Jean-Pierre de Vera, Elke Rabbow, Ute Böttger, Ekaterina Dadachova, Silvano Onofri
The BIOMEX (BIOlogy and Mars Experiment) is part of the European Space Agency (ESA) space mission EXPOSE-R2 in Low-Earth Orbit, devoted to exposing microorganisms for 1.5 years to space and simulated Mars conditions on the International Space Station. In preparing this mission, dried colonies of the Antarctic cryptoendolithic black fungus Cryomyces antarcticus CCFEE 515, grown on martian and lunar analog regolith pellets, were subjected to several ground-based preflight tests, Experiment Verification Tests, and Science Verification Tests (SVTs) that were performed to verify (i) the resistance of our model organism to space stressors when grown on extraterrestrial rock analogues and (ii) the possibility of detecting biomolecules as potential biosignatures...
August 1, 2018: Astrobiology
J H Madden, Lisa Kaltenegger
We present a catalog of spectra and geometric albedos, representative of the different types of solar system bodies, from 0.45 to 2.5 μm. We analyzed published calibrated, uncalibrated spectra, and albedos for solar system objects and derived a set of reference spectra and reference albedos for 19 objects that are representative of the diversity of bodies in our solar system. We also identified previously published data that appear contaminated. Our catalog provides a baseline for comparison of exoplanet observations to 19 bodies in our own solar system, which can assist in the prioritization of exoplanets for time intensive follow-up with next-generation extremely large telescopes and space-based direct observation missions...
July 31, 2018: Astrobiology
Molly N Simon, Sanlyn Buxner, Chris Impey
The topic of solar system formation has become essential to the teaching of astrobiology due to the discovery of more than 3700 exoplanets, some orbiting within their host star's habitable zone. The architecture of planetary systems is more easily understood when students are able to comprehend how solar systems form. There has yet to be a study that addresses the topic of planet formation at the college level using a large sample of introductory astronomy students. We collected responses from students in 13 introductory astronomy and planetary science courses (n = 1050) at the University of Arizona, who each completed 1 of 6 short-answer questions on the topic of planet formation...
July 27, 2018: Astrobiology
Adam H Stevens, Delma Childers, Mark Fox-Powell, Natasha Nicholson, Elisha Jhoti, Charles S Cockell
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...
July 26, 2018: Astrobiology
Melissa A Merrill Floyd, Amy J Williams, Andrej Grubisic, David Emerson
Iron-oxidizing bacteria occupy a distinct environmental niche. These chemolithoautotrophic organisms require very little oxygen (when neutrophilic) or outcompete oxygen for access to Fe(II) (when acidophilic). The utilization of Fe(II) as an electron donor makes them strong analog organisms for any potential life that could be found on Mars. Despite their importance to the elucidation of early life on, and potentially beyond, Earth, many details of their metabolism remain unknown. By using on-line thermochemolysis and gas chromatography-mass spectrometry (GC-MS), a distinct signal for a low-molecular-weight molecule was discovered in multiple iron-oxidizing isolates as well as several iron-dominated environmental samples, from freshwater and marine environments and in both modern and older iron rock samples...
July 25, 2018: Astrobiology
Caleb Scharf
It has been established theoretically that atmospheric thermal tides on rocky planets can lead to significant modifications of rotational evolution, both close to synchronous rotation and at faster rotations if certain resonant conditions are met. Here it is demonstrated that the normally considered dissipative gravitational tidal evolution of rocky planet rotation could, in principle, be "stalled" by thermal tide resonances for Earth-analog worlds in the liquid-water orbital zone of stars more massive than [Formula: see text]...
September 2018: Astrobiology
Eric W Ziegler, Hyo-Joong Kim, Steven A Benner
It has been four decades since formamide was first suggested to perform roles as a precursor and/or a solvent in prebiotic chemistry. However, little work has sought to integrate formamide into larger prebiotic schemes that might create prebiotic RNA, often proposed to have been the first Darwinian biopolymer. Here, we report that formamide can be used as a solvent to perform the Bílik reaction, which uses molybdenum(VI) oxo species as catalysts at near-neutral pH to rearrange branched carbohydrates to give linear carbohydrates; the branched carbohydrates are produced from formaldehyde (HCHO) in alkaline mixtures containing borate, whereas the linear carbohydrates are the precursors needed for ribonucleosides and ribonucleotides...
September 2018: Astrobiology
Jack T O'Malley-James, Lisa Kaltenegger
The high reflection of land vegetation in the near-infrared, the vegetation red edge (VRE), is often cited as a spectral biosignature for surface vegetation on exoplanets. The VRE involves only a few percentage change in reflectivity for a disk-integrated observation of present-day Earth. Here we show that the strength of Earth's VRE has increased over the past ∼500 million years of land plant evolution and may continue to increase as solar luminosity increases and the planet warms, until either vegetation coverage is reduced, or the planet's atmosphere becomes opaque to light reflected off the surface...
September 2018: Astrobiology
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