lpetrich
Contributor
If Mars was once inhabited by organisms, even very primitive ones, organisms that are now extinct, what were the last ones like?
The Last Possible Outposts for Life on Mars | Astrobiology
Attempts to reconstruct a plausible sequence of retreats as Mars becomes more and more hostile.
The authors note that there are some surprisingly early colonists of land: some prokaryotes named Terrabacteria on account of that: the cyanobacteria, the Gram-positive phyla, Chloroflexi / Chloroflexota, and Deinococcus-Thermus / Deinococcota. They diverged as early as 3.5 billion years ago.
The Gram-positive phyla -- Firmicutes / Bacillota, Actinobacteria / Actinomycetota -- are named after their response to a stain that detects their thick cell walls. These cell walls make it easier for these organisms to survive dryness.
Deinococcus radiodurans (ray-enduring fearsome grain) can survive huge doses of ionizing radiation, doses that would kill most other organisms, doses that its ancestors had never experienced. It does so by hyperactive gene repair, repair of damage caused by ionizing radiation, and also dryness, a well-known outcome of being outside of water. So that feature is an adaptation to dryness.
"Representatives of this group possess specific adaptations to land environments such as resistance to desiccation, high salinity, and high UV radiation." There is some possible fossil evidence of land ecosystems around 1.2–1 billion years ago (Gya) and 2.7-2.6 Gya, and freshwater ones around 2.9-2.7 Gya.
"Perhaps not surprisingly, the cyanobacteria, a deeply rooted taxonomic group often found in aquatic environments, include some of the most desiccation-resistant organisms known, which are adapted to survive in the driest regions on Earth (Friedmann, 1980; Friedmann and Ocampo-Friedmann, 1995; Warren-Rhodes et al., 2006; Pointing and Belnap, 2012; Wierzchos et al., 2012b)."
So similar organisms could have inhabited Mars for a long time as the planet dried up.
The Last Possible Outposts for Life on Mars | Astrobiology
Attempts to reconstruct a plausible sequence of retreats as Mars becomes more and more hostile.
The authors note that there are some surprisingly early colonists of land: some prokaryotes named Terrabacteria on account of that: the cyanobacteria, the Gram-positive phyla, Chloroflexi / Chloroflexota, and Deinococcus-Thermus / Deinococcota. They diverged as early as 3.5 billion years ago.
The Gram-positive phyla -- Firmicutes / Bacillota, Actinobacteria / Actinomycetota -- are named after their response to a stain that detects their thick cell walls. These cell walls make it easier for these organisms to survive dryness.
Deinococcus radiodurans (ray-enduring fearsome grain) can survive huge doses of ionizing radiation, doses that would kill most other organisms, doses that its ancestors had never experienced. It does so by hyperactive gene repair, repair of damage caused by ionizing radiation, and also dryness, a well-known outcome of being outside of water. So that feature is an adaptation to dryness.
"Representatives of this group possess specific adaptations to land environments such as resistance to desiccation, high salinity, and high UV radiation." There is some possible fossil evidence of land ecosystems around 1.2–1 billion years ago (Gya) and 2.7-2.6 Gya, and freshwater ones around 2.9-2.7 Gya.
"Perhaps not surprisingly, the cyanobacteria, a deeply rooted taxonomic group often found in aquatic environments, include some of the most desiccation-resistant organisms known, which are adapted to survive in the driest regions on Earth (Friedmann, 1980; Friedmann and Ocampo-Friedmann, 1995; Warren-Rhodes et al., 2006; Pointing and Belnap, 2012; Wierzchos et al., 2012b)."
So similar organisms could have inhabited Mars for a long time as the planet dried up.