Search for life Mars

viking 1 lander s sampling arm scooped soil samples tests (chryse planitia)

the current understanding of planetary habitability—the ability of world develop environmental conditions favorable emergence of life—favors planets have liquid water on surface. requires orbit of planet lie within habitable zone, sun extends beyond venus semi-major axis of mars. during perihelion, mars dips inside region, mars s thin (low-pressure) atmosphere prevents liquid water existing on large regions extended periods. past flow of liquid water demonstrates planet s potential habitability. recent evidence has suggested water on martian surface may have been salty , acidic support regular terrestrial life.

the lack of magnetosphere , extremely thin atmosphere of mars challenge: planet has little heat transfer across surface, poor insulation against bombardment of solar wind , insufficient atmospheric pressure retain water in liquid form (water instead sublimes gaseous state). mars nearly, or perhaps totally, geologically dead; end of volcanic activity has apparently stopped recycling of chemicals , minerals between surface , interior of planet.

detection of impact glass deposits (green spots) @ alga crater, possible site preserved ancient life

in situ investigations have been performed on mars viking landers, spirit , opportunity rovers, phoenix lander, , curiosity rover. evidence suggests planet once more habitable today, whether living organisms ever existed there remains unknown. viking probes of mid-1970s carried experiments designed detect microorganisms in martian soil @ respective landing sites , had positive results, including temporary increase of co2 production on exposure water , nutrients. sign of life later disputed scientists, resulting in continuing debate, nasa scientist gilbert levin asserting viking may have found life. re-analysis of viking data, in light of modern knowledge of extremophile forms of life, has suggested viking tests not sophisticated enough detect these forms of life. tests have killed (hypothetical) life form. tests conducted phoenix mars lander have shown soil has alkaline ph , contains magnesium, sodium, potassium , chloride. soil nutrients may able support life, life still have shielded intense ultraviolet light. recent analysis of martian meteorite eeta79001 found 0.6 ppm clo−

4, 1.4 ppm clo−

3, , 16 ppm no−

3, of martian origin. clo−

3 suggests presence of other highly oxidizing oxychlorines, such clo−

2 or clo, produced both uv oxidation of cl , x-ray radiolysis of clo−

4. thus, highly refractory and/or well-protected (sub-surface) organics or life forms survive.

a 2014 analysis of phoenix wcl showed ca(clo

4)

2 in phoenix soil has not interacted liquid water of form, perhaps long 600 myr. if had, highly soluble ca(clo

4)

2 in contact liquid water have formed caso

4. suggests severely arid environment, minimal or no liquid water interaction.

scientists have proposed carbonate globules found in meteorite alh84001, thought have originated mars, fossilized microbes extant on mars when meteorite blasted martian surface meteor strike 15 million years ago. proposal has been met skepticism, , exclusively inorganic origin shapes has been proposed.

small quantities of methane , formaldehyde detected mars orbiters both claimed possible evidence life, these chemical compounds break down in martian atmosphere. alternatively, these compounds may instead replenished volcanic or other geological means, such serpentinization.

impact glass, formed impact of meteors, on earth can preserve signs of life, has been found on surface of impact craters on mars. likewise, glass in impact craters on mars have preserved signs of life if life existed @ site.

in may 2017, evidence of earliest known life on land on earth may have been found in 3.48-billion-year-old geyserite , other related mineral deposits (often found around hot springs , geysers) uncovered in pilbara craton of western australia. these findings may helpful in deciding best search signs of life on planet mars.