Lichens, cyanobacteria and molds growing in humidity of simulated Martian atmosphere: Difference between revisions
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Lichens, cyanobacteria and molds growing in humidity of simulated Martian atmosphere (edit)
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A series of experiments by DLR (German aerospace company) in Mars simulation chambers and on the ISS show that some Earth life (Lichens and strains of chrooccocidiopsis, a green algae) can survive Mars surface conditions and photosynthesize and metabolize, slowly, in absence of any water at all. They could make use of the humidity of the Mars atmosphere.<ref name="dlrMarsStudy">[http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10081/151_read-3409/ Surviving the conditions on Mars] DLR, 26 April 2012</ref><ref name="sciencedirect.com">{{cite journal|url = http://www.sciencedirect.com/science/article/pii/S1754504812000098 | doi=10.1016/j.funeco.2012.01.008 | volume=5 | issue=4 | title=Lichens as survivors in space and on Mars | year=2012 | journal=Fungal Ecology | pages=472–479 | last1 = de Vera | first1 = Jean-Pierre}}</ref><ref name="norlx51.nordita.org">R. de la Torre Noetzel, F.J. Sanchez Inigo, E. Rabbow, G. Horneck, J. P. de Vera, L.G. Sancho [http://norlx51.nordita.org/~brandenb/astrobiology/EANA2012/single_abstracts/Delatorre.pdf Survival of lichens to simulated Mars conditions] {{webarchive|url=https://web.archive.org/web/20130603191033/http://norlx51.nordita.org/~brandenb/astrobiology/EANA2012/single_abstracts/Delatorre.pdf |date=2013-06-03 }}</ref><ref name="Issue 1 2012, Pages 102">{{cite journal|url = http://www.sciencedirect.com/science/article/pii/S0032063312002425 | doi=10.1016/j.pss.2012.08.005 | bibcode=2012P&SS...72..102S | volume=72 | issue=1 | title=The resistance of the lichen Circinaria gyrosa (nom. provis.) towards simulated Mars conditions—a model test for the survival capacity of an eukaryotic extremophile | year=2012 | journal=Planetary and Space Science | pages=102–110 | last1 = Sánchez | first1 = F.J.}}</ref><ref name="BilliViaggiu2011">{{cite journal|url=https://scholar.google.com/scholar_url?url=http://www.researchgate.net/profile/Charles_Cockell/publication/49810974_Damage_escape_and_repair_in_dried_Chroococcidiopsis_spp._from_hot_and_cold_deserts_exposed_to_simulated_space_and_martian_conditions/links/0c960530543245cde9000000.pdf&hl=en&sa=T&oi=gsb-gga&ct=res&cd=1&ei=M2AqVeLzG-fq0AG5xYGACA&scisig=AAGBfm1aHrkKehQaYpPYGQ9mjRxVTxPS0Q|last1=Billi|first1=Daniela|last2=Viaggiu|first2=Emanuela|last3=Cockell|first3=Charles S.|last4=Rabbow|first4=Elke|last5=Horneck|first5=Gerda|last6=Onofri|first6=Silvano|title=Damage Escape and Repair in DriedChroococcidiopsisspp. from Hot and Cold Deserts Exposed to Simulated Space and Martian Conditions|journal=Astrobiology|volume=11|issue=1|year=2011|pages=65–73|issn=1531-1074|doi=10.1089/ast.2009.0430|pmid=21294638|bibcode=2011AsBio..11...65B}}</ref> Though the absolute humidity is low, the relative humidity at night reaches 100% because of the large day / night swings in atmospheric pressure and temperature. This is relevant to the search for native life on Mars and also to planetary protection, the need to protect Mars from Earth life if we wish to study native life in the habitats in its original state.
==Lichens relying on
The lichens studied in these experiments have protection from UV light due to special pigments only found in lichens, such as parietin and antioxidants such as b-carotene in epilithic lichens. This gives them enough protection to tolerate the light levels in conditions of partial shade in the simulation chambers and make use of the light to photosynthesize. Indeed, UV protection pigments have been suggested as potential biomarkers to search for on Mars.<ref>"Solar radiation is the primary energy source for surface planetary life, so that pigments are fundamental components of any surface-dwelling organism. They may therefore have evolved in some form on Mars as they did on Earth." {{cite journal | doi = 10.1017/S1473550402001039 | volume=1 | pages=39 | title=Pigmentation as a survival strategy for ancient and modern photosynthetic microbes under high ultraviolet stress on planetary surfaces | year=2002 | journal=International Journal of Astrobiology | last1 = Wynn-Williams | first1 = D.D. | last2 = Edwards | first2 = H.G.M. | last3 = Newton | first3 = E.M. | last4 = Holder | first4 = J.M.| bibcode=2002IJAsB...1...39W }}</ref>
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When exposed to full UV levels in a 34-day experiment in a Mars simulation chamber at DLR, the fungus component of the lichen Pleopsidium chlorophanum died, and it wasn't clear if the algae component was still photosynthesizing.
However, when partially shaded from the UV light, as
In this experiment the temperature varied between +21 °C and -50 °C. Relative humidity is higher in cold air, for the same concentrations of water vapour, and as the temperature varied, the relative humidity varied between 0.1% and 75%. The atmosphere consisted of 5% CO<sub>2</sub>,4%N<sub>2</sub>, and 1% O<sub>2</sub> at 800 Pa or about 0.79% of Earth's sea level atmospheric pressure. This approximates conditions that are encountered in the equatorial and lower lattitude regions of Mars.
The experimenters concluded that it is likely that some lichens and cyanobacteria can adapt to Mars conditions, taking advantage of the night time humidity, and that it is possible that life from early Mars could have adapted to these conditions and still survive today in microniches on the surface.
==Black fungi and black yeast relying on 100% night time humidity==
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