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Life on Mars
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An artist's impression of what Mars' surface and atmosphere might look like, if Mars were terraformed.
Another view of a terraformed Mars
For centuries people have speculated about the possibility of life on Mars due to the planet's proximity and similarity to Earth. Serious searches for evidence of life began in the 19th century, and they continue today via telescopic investigations and landed missions. While early work focused on phenomenology and bordered on fantasy, modern scientific inquiry has emphasized the search for water, chemical biosignatures in the soil and rocks at the planet's surface, and biomarker gases in the atmosphere.Mars is of particular interest for the study of the origins of life because of its similarity to the early Earth. This is especially so since Mars has a cold climate and lacks plate tectonics or continental drift, so it has remained almost unchanged since the end of the Hesperian period. At least two thirds of Mars's surface is more than 3.5 billion years old, and Mars may thus hold the best record of the prebiotic conditions leading to abiogenesis, even if life does not or has never existed there. It remains an open question whether life currently exists on Mars or has existed there in the past, and fictional Martians have been a recurring feature of popular entertainment of the 20th and 21st centuries.On January 24, 2014, NASA reported that current studies on the planet Mars by the Curiosity and Opportunity rovers will now be searching for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic, and/or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable. The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on the planet Mars is now a primary NASA objective.
^ Mumma, Michael J. (January 8, 2012). "The Search for Life on Mars". Origin of Life Gordon Research Conference. Galveston, TX.
^ McKay, Christopher P.; Stoker, Carol R. (1989). "The early environment and its evolution on Mars: Implication for life". Reviews of Geophysics 27 (2): 189–214. Bibcode:1989RvGeo..27..189M. doi:10.1029/RG027i002p00189.
^ Gaidos, Eric; Selsis, Franck (2007). "From Protoplanets to Protolife: The Emergence and Maintenance of Life". Protostars and Planets V: 929–44. arXiv:astro-ph/0602008. Bibcode:2007prpl.conf..929G.
^ a b Grotzinger, John P. (January 24, 2014). "Introduction to Special Issue - Habitability, Taphonomy, and the Search for Organic Carbon on Mars". Science 343 (6169): 386–387. Bibcode:2014Sci...343..386G. doi:10.1126/science.1249944.
^ Various (January 24, 2014). "Special Issue - Table of Contents - Exploring Martian Habitability". Science 343 (6169): 345–452.
^ Various (January 24, 2014). "Special Collection - Curiosity - Exploring Martian Habitability". Science.
^ Grotzinger, J. P.; Sumner, D. Y.; Kah, L. C.; Stack, K.; Gupta, S.; Edgar, L.; Rubin, D.; Lewis, K.; Schieber, J. et al. (January 24, 2014). "A Habitable Fluvio-Lacustrine Environment at Yellowknife Bay, Gale Crater, Mars". Science 343 (6169, number 6169): 1242777. doi:10.1126/science.1242777.
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