Did Earth's Life Originate on Mars?

A paper published in Astrobiology on 2022-07-11 suggests “Resolving the History of Life on Earth by Seeking Life As We Know It on Mars” (full text available at the link). The abstract argues:

An origin of Earth life on Mars would resolve significant inconsistencies between the inferred history of life and Earth’s geologic history. Life as we know it utilizes amino acids, nucleic acids, and lipids for the metabolic, informational, and compartment-forming subsystems of a cell. Such building blocks may have formed simultaneously from cyanosulfidic chemical precursors in a planetary surface scenario involving ultraviolet light, wet-dry cycling, and volcanism. On the inferred water world of early Earth, such an origin would have been limited to volcanic island hotspots. A cyanosulfidic origin of life could have taken place on Mars via photoredox chemistry, facilitated by orders-of-magnitude more sub-aerial crust than early Earth, and an earlier transition to oxidative conditions that could have been involved in final fixation of the genetic code. Meteoritic bombardment may have generated transient habitable environments and ejected and transferred life to Earth. Ongoing and future missions to Mars offer an unprecedented opportunity to confirm or refute evidence consistent with a cyanosulfidic origin of life on Mars, search for evidence of ancient life, and constrain the evolution of Mars’ oxidation state over time. We should seek to prove or refute a martian origin for life on Earth alongside other possibilities.

The paper concludes:

Early Mars likely offered more opportunity for cyanosulfidic prebiotic chemistry to cross the threshold to life than early Earth, including cold temperatures to stabilize accumulation of organics and orders-of-magnitude more land area. Mars’ earlier transition to oxidizing conditions could have played a role in fixation of the genetic code on a timeline consistent with genetic evidence. Furthermore, all steps in the meteoritic transfer of life from Mars to Earth have been theoretically or experimentally verified, and such a transfer is consistent with genetic evidence. Mars 2020 and the planned Rosalind Franklin rover are well positioned to test the plausibility of a cyanosulfidic origin of life on Mars, search for ancient evidence of life, and constrain the evolution of Mars’ oxidation state over time. Unlike Earth, where ancient rocks are rare, on Mars we can access rocks across nearly the full 4.5 billion year history of that planet (Bouvier et al., 2018). Despite the modern thin (1% that of Earth) atmosphere and cold average surface temperature (-60°C), the subsurface of Mars likely remains habitable (Jones et al., 2011). Future missions, with access to special regions, including deep drilling to seek habitable environments in the subsurface, may be required to target any extant life and unambiguously determine whether life as we know it exists on Mars today and, if so, whether it is related to us.

Maybe we’re all martians.