Abstract-Asteroids and their fragments have impacted the Earth for the last 4.5 Gyr. Carbonaceous meteorites are known to contain a wealth of indigenous organic molecules, including amino acids, which suggests that these meteorites could have been an important source of prebiotic organic material during the origins of life on Earth and possibly elsewhere. We report the detection of extraterrestrial amino acids in thermally altered type 3 CV and CO carbonaceous chondrites and ureilites recovered from Antarctica. The amino acid concentrations of the thirteen Antarctic meteorites ranged from 300 to 3200 parts-per-billion (ppb), generally much less abundant than in amino acid-rich CI, CM, and CR carbonaceous chondrites that experienced much lower temperature aqueous alteration on their parent bodies. In contrast to low-temperature aqueously altered meteorites that show complete structural diversity in amino acids formed predominantly by Streckercyanohydrin synthesis, the thermally altered meteorites studied here are dominated by small, straightchain, amine terminal (n-x-amino) amino acids that are not consistent with Strecker formation. The carbon isotopic ratios of two extraterrestrial n-x-amino acids measured in one of the CV chondrites (d 13C approximately )25&) are consistent with 13 C-depletions observed previously in hydrocarbons produced by Fischer-Tropsch type reactions. The predominance of n-x-amino acid isomers in thermally altered meteorites hints at cosmochemical mechanisms for the preferential formation and preservation of a small subset of the possible amino acids.

Abstract. When hydrogen, nitrogen and CO are exposed to amorphous iron silicate surfaces at temperatures between 500-900 K a carbonaceous coating forms via Fischer-Tropsch type reactions. Under normal circumstances such a coating would impede or stop further reaction. However, we find that this coating is a better catalyst than the amorphous iron silicates that initiate these reactions. Formation of a self-perpetuating catalytic coating on grain surfaces could explain the rich deposits of macromolecular carbon found in primitive meteorites and would imply that protostellar nebulae should be rich in organic material.

The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission described herein has been selected for flight to Venus as part of the NASA Discovery Program. DAVINCI will be the first mission to Venus to incorporate science-driven flybys and an instrumented descent sphere into a unified architecture. The anticipated scientific outcome will be a new understanding of the atmosphere, surface, and evolutionary path of Venus as a possibly once-habitable planet and analog to hot terrestrial exoplanets. The primary mission design for DAVINCI as selected features a preferred launch in summer/fall 2029, two flybys in 2030, and descent-sphere atmospheric entry by the end of 2031. The in situ atmospheric descent phase subsequently delivers definitive chemical and isotopic composition of the Venus atmosphere during an atmospheric transect above Alpha Regio. These in situ investigations of the atmosphere and near-infrared (NIR) descent imaging of the surface will complement remote flyby observations of the dynamic atmosphere, cloud deck, and surface NIR emissivity. The overall mission yield will be at least 60 Gbits (compressed) new data about the atmosphere and near surface, as well as the first unique characterization of the deep atmosphere environment and chemistry, including trace gases, key stable isotopes, oxygen fugacity, constraints on local rock compositions, and topography of a tessera.

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The Venus atmosphere is of significant interest yet only rudimentary solid data have been gathered about its composition and chemistry. These measurements are scattered through time and place and are limited by parameters such as resolution and error margins as well as reinterpretations. This paper presents an extensive compilation of published in situ data for the atmospheric composition of Venus. It also includes remotely gathered measurements and some extrapolated and modeled data for the lower atmosphere. The composition tables are divided in four categories: noble gases, reactive gases, noble, and nonnoble isotopes. These tables were first presented in 2016 within the scientific heritage appendix of the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission proposal. These tables provide respective measurements, error margins, techniques, altitudes, instruments, mission, and references. The objective of this paper is to provide a simple, comprehensive list of available measurements to date, in particular the in situ data, to serve as a quick overall Venus atmosphere data reference.

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