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Most chemical reactions on asteroids, from which meteors and meteorites originate, are hypothesized to occur primarily in the solid mixtures. Some secondary chemical reactions may have occurred during the periods of the aqueous alteration of the asteroids. A myriad of organic compounds have been isolated from the meteorites, but the chemical conditions during which they were formed are only partially elucidated. In this paper, we propose that numerous meteoritic organic compounds were formed by the solventless and solid-state reactions that were only recently explored in conjunction with the green chemistry. A typical solventless approach exploits the phenomenon of the mixed melting points. As the solid materials are mixed together, the melting point of the mixture becomes lower than the melting points of its individual components. In some cases, the entire mixture may melt upon mixing. These reactions could then occur in a melted state. In the traditional solid-state reactions, the solids are mixed together, which allows for the intimate contact of the reactants, but the reaction occurs without melting. We have shown various examples of the known solventless and solid-state reactions that are particularly relevant to the meteoritic chemistry. We have also placed them in a prebiotic context and evaluated them for their astrobiological significance. [ABSTRACT FROM PUBLISHER]

The connection between astrobiology and green chemistry represents a new approach to sustainability of organic matter on asteroids or similar bodies. Green chemistry is chemistry which is environmentally friendly. One obvious way for chemistry to be green is to use water as a solvent, instead of more toxic organic solvents. Many astrobiological reactions occur in the aqueous medium, for example in the prebiotic soup or during the aqueous alteration period on asteroids. Thus any advances in the green organic reactions in water are directly applicable to astrobiology. Another green chemistry approach is to abolish use of toxic solvents. This can be accomplished by carrying out the reactions without a solvent in the solventless or solid-state reactions. The advances in these green reactions are directly applicable to the chemistry on asteroids during the periods when water was not available. Many reactions on asteroids may have been done in the solid mixtures. These reactions may be responsible for a myriad of organic compounds that have been isolated from the meteorites. [ABSTRACT FROM AUTHOR]

Although the habitability of early Mars is now well established, its suitability for conditions favorable to an independent origin of life (OoL) has been less certain. With continued exploration, evidence has mounted for a widespread diversity of physical and chemical conditions on Mars that mimic those variously hypothesized as settings in which life first arose on Earth. Mars has also provided water, energy sources, CHNOPS elements, critical catalytic transition metal elements, as well as B, Mg, Ca, Na and K, all of which are elements associated with life as we know it. With its highly favorable sulfur abundance and land/ocean ratio, early wet Mars remains a prime candidate for its own OoL, in many respects superior to Earth. The relatively well-preserved ancient surface of planet Mars helps inform the range of possible analogous conditions during the now-obliterated history of early Earth. Continued exploration of Mars also contributes to the understanding of the opportunities for settings enabling an OoL on exoplanets. Favoring geochemical sediment samples for eventual return to Earth will enhance assessments of the likelihood of a Martian OoL. [ABSTRACT FROM AUTHOR]