Lichens, cyanobacteria and molds growing in humidity of simulated Martian atmosphere: Difference between revisions

The experimenters concluded that these black fungi can survive in a Mars environment.<ref name="ZakharovaMarzban2014">{{cite journal|url=http://www.nature.com/srep/2014/140529/srep05114/full/srep05114.html|last1=Zakharova|first1=Kristina|last2=Marzban|first2=Gorji|last3=de Vera|first3=Jean-Pierre|last4=Lorek|first4=Andreas|last5=Sterflinger|first5=Katja|title=Protein patterns of black fungi under simulated Mars-like conditions|journal=Scientific Reports|volume=4|pages=5114|year=2014|issn=2045-2322|doi=10.1038/srep05114|pmid=24870977|pmc=4037706|quote="The results achieved from our study led to the conclusion that black microcolonial fungi can survive in Mars environment."|bibcode=2014NatSR...4E5114Z}}</ref>

 

 

In experimental studies of salt pillars in the Atacama desert, microbes are able to access liquid at extremely low relative humidities due to micropores in the salt structures. They do this through spontaneous capillary condensation, at relative humidities far lower than the deliquescence point of NaCl of 75%.<ref>{{cite web|last1=Bortman|first1=Henry|title=Islands of Life, Part V|url=http://www.astrobio.net/topic/origins/extreme-life/islands-of-life-part-v/|website=Astrobiology Magazine (NASA)|date=Jul 25, 2011}}</ref>

 

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The researchers, Wierzchos et al., did detailed studies with scanning electron microscopes. At 75% relative humidity then brine was abundant inside the salt pillars. As the humidity was reduced, even at 30% RH, the cyanobacteria aggregates shrunk due to water loss, but still there were small pockets of brine in the salt pillars.<ref name="WierzchosDavila2012">{{cite journal|url=http://www.biogeosciences.net/9/2275/2012/bg-9-2275-2012.pdf|last1=Wierzchos|first1=J.|last2=Davila|first2=A. F.|last3=Sánchez-Almazo|first3=I. M.|last4=Hajnos|first4=M.|last5=Swieboda|first5=R.|last6=Ascaso|first6=C.|title=Novel water source for endolithic life in the hyperarid core of the Atacama Desert|journal=Biogeosciences|volume=9|issue=6|year=2012|pages=2275–2286|issn=1726-4189|doi=10.5194/bg-9-2275-2012|bibcode=2012BGeo....9.2275W}}</ref>

 

{{quote|"Endolithic communities inside halite pinnacles in the Atacama Desert take advantage of the moist conditions that are created by the halite substrate in the absence of rain, fog or dew. The tendency of the halite to condense and retain liquid water is enhanced by the presence of a nano-porous phase with a smooth surface skin, which covers large crystals and fills the larger pore spaces inside the pinnacles... Endolithic microbial communities were observed as intimately associated with this hypothetical nano-porous phase. While halite endoliths must still be adapted to stress conditions inside the pinnacles (i.e. low water activity due to high salinity), these observations show that hygroscopic salts such as halite become oasis for life in extremely dry environments, when all other survival strategies fail.<br><br>Our findings have implications for the habitability of extremely dry environments, as they suggest that salts with properties similar to halite could be the preferred habitat for life close to the dry limit on Earth and elsewhere. It is particularly tempting to speculate that the chloride-bearing evaporites recently identified on Mars may have been the last, and therefore most recently inhabited, substrate as this planet transitioned from relatively wet to extremely dry conditions"}}

 

Microbes also inhabit Gypsum deposits (CaSO₄.2H₂O), however Gypsum doesn't deliquesce. Researchers found that the regions of the desert that had microbial colonies within the gypsum correlated with regions with over 60% relative humidity for a significant part of the year. They also found that the microbes imbibed water whenever the humidity increased above 60% and gradually became desiccated when it was below that figure.<ref name="WierzchosCámara2011">{{cite journal|url=https://www.researchgate.net/profile/Alfonso_Davila/publication/45797377_Microbial_colonization_of_Ca-sulfate_crusts_in_the_hyperarid_core_of_the_Atacama_Desert_implications_for_the_search_for_life_on_Mars/links/0912f50e37831ae515000000.pdf|last1=Wierzchos|first1=J.|last2=Cámara|first2=B.|last3=De Los Ríos|first3=A.|last4=Davila|first4=A. F.|last5=Sánchez Almazo|first5=I. M.|last6=Artieda|first6=O.|last7=Wierzchos|first7=K.|last8=Gómez-Silva|first8=B.|last9=Mckay|first9=C.|last10=Ascaso|first10=C.|title=Microbial colonization of Ca-sulfate crusts in the hyperarid core of the Atacama Desert: implications for the search for life on Mars|journal=Geobiology|volume=9|issue=1|year=2011|pages=44–60|issn=1472-4677|doi=10.1111/j.1472-4669.2010.00254.x|pmid=20726901}}</ref>