Astrobiology of hot springs on early Earth and Mars

CAMPBELL, K.; WESTALL, F.; KRANENDONK, M.; GUIDO, D.

Conferencia; Australian Space Research Conference; 2016

How might understanding the origin, early evolution and current distribution of life increase prospects of finding it elsewhere? Is or was there ever life on Mars? Mars missions have focused on habitability in surface (paleo)environments by ?following the water?. Extremophiles on Earth are considered analogous to what might be encountered on other worlds, because they survive in extremes that mimic conditions there. Distributions of aqueous minerals have been mapped on Mars, indicating that >3 billion years ago liquid water and punctuated hydrothermal activity from volcanism and extraterrestrial impacts could have provided nutrients and energy to sustain metabolism, as it did similarly on Earth around the same time. Furthermore, some have suggested that life originated on land in hot springs rather than in the oceans.  The next rovers will engage in explicit pursuit of fossil signs of life, in locations where both its potential for preservation and detection are maximized. This is a challenge because organic matter at the martian surface may not have persisted, yet morphology alone cannot verify biosignature potential. Conversely rapid mineral entombment of microorganisms bathed by silica-charged, thermal spring fluids may preserve microbial textures well, and even have shielded microbes from harsh surface conditions on early Earth and Mars. Whether rovers search for biosignatures in lake sediments or siliceous hot spring (sinter) outcrops, the top two preferred landing site candidates to date, targeted samples are to be cached and eventually returned to Earth for detailed laboratory study.  Terrestrial hot spring environment models indicate diverse microbial textures from hot vent to cool marsh areas. Similar features have been found in the setting of the oldest fossils (3.48 billion year old cherts, Western Australia), and in the Columbia Hills opaline silica deposit, Mars. Hence, terrestrial hot springs and their sinter deposits are important extreme environment analogs for astrobiology.