The origin of life as a planetary phenomenon

Abstract

We advocate an integrative approach between laboratory experiments in prebiotic chemistry and geologic, geochemical, and astrophysical observations to help assemble a robust chemical pathway to life that can be reproduced in the laboratory. The cyanosulfidic chemistry scenario described here was developed by such an integrative iterative process. We discuss how it maps onto evolving planetary surface environments on early Earth and Mars and the value of comparative planetary evolution. The results indicate that Mars can offer direct evidence for geochemical conditions similar to prebiotic Earth, whose early record has been erased. The Jezero crater is now the chosen landing site for NASA’s Mars 2020 rover, making this an extraordinary opportunity for a breakthrough in understanding life’s origins.

Photochemistry of Anoxic Abiotic Habitable Planet Atmospheres: Impact of New H2O Cross Sections

“…Alternately, Mars may provide a touchstone. Like Earth, early Mars should have hosted an abiotic ocean under an anoxic atmosphere, but unlike Earth, the lack of tectonic activity and hydrology means that geological evidence from this epoch may be preserved (Citron et al 2018;Sasselov et al 2020). Are there geological fingerprints of the presence or absence of redox balance (e.g., Figure 6.…”

Probing space to understand Earth

“…The Mars 2020 rover, in particular, will acquire a series of samples to be returned to Earth through a Mars sample-return mission orchestrated by NASA and the ESA. These samples could provide critical constraints on the timing and magnitude of Solar System events that directly impacted Earth's history, including, possibly, the origins of life 118,209 . NASA's Psyche orbiter will launch in 2022 to explore the metal-rich 16 Psyche asteroid, seeking to answer fundamental questions about planetary cores and possibly offering our first direct look at a protoplanetary core fragment.…”

“…Samples from small bodies, such as iron meteorites, and Mars could be used to identify and isolate abiotic elemental cycling (such as the Martian phosphorus cycle 117 ) from biological effects. Information about extraterrestrial element cycles can then be used to understand the contribution of abiotic cycling on early Earth and the potential availability of key elements when life first arose 118 . Earth-sized and super-Earth-sized planets also provide a wealth of analogues for prebiotic Earth volatile cycles in chemical and mass parameter spaces that are not available in our Solar System 119 (Box 1).…”

Depsipeptide nucleic acids: prebiotic formation, oligomerization, and self-assembly of a new candidate proto-nucleic acid

“…These bases were chosen because they are formed in the same model prebiotic reaction, 39 and because cyanuric acid, with an acceptor-donor-acceptor hydrogen-bonding pattern, can form aqueous hexad-based supramolecular assemblies by Watson-Crick-like pairing with derivatives of melamine (donor-acceptor-donor), 11 as well as supramolecular polymers with homo-adenine (donoracceptor) RNA or PNA oligomers. [40][41][42] Ferrocyanide was chosen as the cyanide source because iron(II) cyanide complexes have been noted as compounds that were likely present on the early Earth (due to the inferred abundance of iron(II) and cyanide, 43 or due to their direct detection in meteorites 44 ) which can act as a slowly-releasing cyanide reservoir. In this regard, ferrocyanide has been successfully used in aqueous Strecker reactions as a "green" alternative to methods that employ more toxic cyanide sources.…”