PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.Womens Sperry Top Sider Slip On Bluefish Boat Shoes Size 6M with Tag and Box , J. Crew Women's Brown Patent Leather Slip On Squared Toe Ballet Flats Size 9.5 , Indian Rajasthani Black Color With Skyblue Thread Work Mirror juti Mojari Women , Donald J Pliner Women's Brown Synthetic Closed Toe Loafer Shoes Size 7.5 MNew Orthofeet Women Wichita Tan Washable Shoes Sz 6.5 4E XXW NO INSOLESAmerican Eagle Ballet Flat - Size 8 - NWT - Faux Fur Inside , COLE HAAN Air Reva Shearling Mules, Brown Waterproof Leather , Naturalizer Artesia Mary Jane Split Toe Womens Brown Leather Slip On Shoes Sz 8NSofft Women's Brown/Multi Color Clogs 9 NVince Nina D'orsay Leather Flats Women Black 9M ITALY , Black w/Bronze Gold Snake Python Print DANSKO Slip ON Shoes US 8.5 - 9ARRAY Womens Whirlwind Leather Closed Toe Loafers, chp lther, Size 9.0 aP9SLacoste Women's Marice Canvas Slip On, Navy Canvas, 9 M USVia Spiga Womens V-Raine3 Grey Leather Fashion Shoes Size 9 (336077) , NIKE 324751-141 MUSIQUE IV Women White Leather Dance Sneaker Shoe 8M , WOMANS SZ 7.5 BLUE COLOR SNEAKER SHOES BY ROUGE HELIUM DENIM , Pedro Garcia Studded Leather Flats with Frayed Trim in Brown Size: 39.5 EUR , GOLDTOE $65 MEN SHOES SLIPPERS Cotton Slippers SZ 10-11 Gray Memory Foam E15 , Fila Women's Memory Kameo 4 Cross Trainer, Castlerock/Black/White, 9.5 Medium US , RYKA Womens Slip On Mules Slide Lght Beige Athletic Sneakers STRETCH Sz 8LIZ CLAIBORNE Women's Warwick Burgundy Velvet Gold Accent Sneaker Shoe Size 8.5Women's Varda Black Loafers Size 36 Beautiful FlatsWomen's Derbies Elegant And Sturdy Package Flats , Lhasa Apso Dog Pattern Print Car Seat Covers-Free Shipping , Women Adidas Cosmic 2 SL Running CQ1713 Aqua Petrol Night 100% Original New , VANS New Old Skool Blanket Weave Vault Lady size 7Puma Roma Womens Athletic Shoes Sz 9 Sneakers White Red & Blue , Women's Puma Etolie SH Puma Silver/Limeade/White 348273 11 Brand New In Box , Pre Owned NIB Nike Initiators. White w/ pink trim. Womens 8.5Saucony Women's ProGrid Guide 4 Silver Pink Black Running Shoes 10090-2
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."