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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[[Image:Martian conditions in miniature (7494313830) (2).jpg|thumb|Martian conditions in miniature - In the Mars simulation chamber, DLR researchers recreated the atmospheric composition and pressure, the planet's surface, the temperature cycles and the solar radiation incident on the surface. The activity of polar and alpine lichen was investigated under these conditions.]]
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 over 70% as measured directly in Gale Crater by Curiosity, because of the large day / night swings in atmospheric pressure and temperature. It may well reach much closer to 100% in regions where frosts are seen (including the [[Viking 2]] lander site) and where ground hugging mists form, including equatorial regions in Valles Marineres and the Hellas basin<ref name=Martínez2017/>. 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
Any photosynthetic life on Mars would have to cope with the strong UV light, which is not much filtered by the thin Mars atmosphere. 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.
This was an experiment without the day night temperature cycles of Mars and the lichens were kept in a desiccated state so it didn't test their ability to survive in niche habitats on Mars. This greatly exceeded the post flight viability of any of the other organisms tested in the experiment.<ref name="Brandtde Vera2014">{{cite journal|url=http://elib.dlr.de/90411/1/Annette-Brandt-download.php.pdf|last1=Brandt|first1=Annette|last2=de Vera|first2=Jean-Pierre|last3=Onofri|first3=Silvano|last4=Ott|first4=Sieglinde|title=Viability of the lichen Xanthoria elegans and its symbionts after 18 months of space exposure and simulated Mars conditions on the ISS|journal=International Journal of Astrobiology|year=2014|pages=1–15|issn=1473-5504|doi=10.1017/S1473550414000214|volume=14|issue=3|bibcode=2015IJAsB..14..411B}}</ref>
==Lichens relying on 75% night time humidity to metabolize and photosynthesize==
Another study in 2014 by German aerospace DLR in a Mars simulation chamber used the lichen Pleopsidium chlorophanum. This lives in the most Mars like environmental conditions on Earth, at up to 2000 meters in Antarctica. It is able to cope with high UV, low temperatures and dryness. It is mainly found in cracks, where just a small amount of scattered light reaches it. This is probably adaptive behaviour to protect it from UV light and desiccation. It remains metabolically active in temperatures down to -20 C, and can absorb small amounts of liquid water in an environment with ice and snow.<ref name="DLRLichenHabitable"/>
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{{quote|The work presented here and work conducted in deserts around the world in the past 40 years, indicate that any putative microbial life on Mars would have likely colonized the insides of rocks and crusts, as they provide natural shelter against harmful radiation and also enhance the moisture conditions on a micro scale. Sulfate and chloride evaporitic deposits have been suggested as a possible oasis for an extant biota, or the last refuge for an extinct biota on the surface of Mars). In this context, terrestrial evaporite rocks, including the Ca-sulfate crusts of the dry core of the Atacama Desert as key terrestrial analogs of Martian aqueous deposits, might prove useful for assessing the habitability of the Martian surface, and develop or improve current strategies for the search for life on Mars}}
==
[[Image:Curiosity humidity measurements.gif|thumb|Upper chart shows the humidity, lower chart shows the volume mixing ratio in parts per million, both measurements taken at the same time, height 1.6 meters above the ground]][[Image:Curiosity temperature measurements.gif|thumb|Upper chart shows the average temperature, lower chart shows the range, the warm orange and red colours are Curiosity annual readings, the blue and green dcolours are for the Viking landers and the gray colours are for the Phoenix lander]]
This section is based on the survey article by Martinez et al, "The modern near-surface martian climate: A review of in-situ meteorological data from Viking to Curiosity."<ref name=Martínez2017>Martínez, G. M., C. N. Newman, A. De Vicente-Retortillo, E. Fischer, N. O. Renno, M. I. Richardson, A. G. Fairén et al. [https://link.springer.com/article/10.1007/s11214-017-0360-x "The modern near-surface martian climate: A review of in-situ meteorological data from Viking to Curiosity."] Space Science Reviews 212, no. 1-2 (2017): 295-338.</ref>
The humidity variations on Mars are mainly due to the daily and seasonal variations of temperature of the air. Colder air has a higher relative humidity for the same water content.
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