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.02-3242 French Sole Sloop Flat Women's Flat SIZE 9.5Women's Earth Origins Erika Loafers COMFORT Shoes SZ 8.5 M Black Leather D8396 , SAS Shoes Women's Penny Loafer Moc Toe Hand Sewn Comfort Beige Leather 7 M , Zoe & Zac Brown Flats - Size 6JIL SANDER Womens Brown Leather Pointed-Toe Flats 8-38 , Seychelles Shoes Size 10 Green Tweed Slip On Bow Flats , Tahari Womens Gibson Leather Ballerina Flats Round Toe Beige Nude With Bow 6.5 MPrimigi Sneakers Xena 38N L 7 Multi Silver , Easy Spirit Traveltime Comfort Flat Mules Tan White 7.5 WIDE SAVE HERE BIG�� , Alegria by PG Lite Mary Jane Clogs Shiny Black Size 37 US Size 6 PAL-411 , CROCS Jibbitz Kilby Women's Ocean/Blue Relaxed Fit Clog Mules Shoes Size 9 NEWWomens Leather Rivets High Tops Athletic Sneakers Flat Heels Leisure College New , CREATIVE RECREATION GOLD/WHITE/BLK HIGH TOPS SIZE 7L , Saucony Womens Gridsd LightTan Running Shoes Size 9 (362418) , ROCKET DOG Women Athletic Walking Shoes Size 8.5 Silver Leather/MeshHawkwell Women's Flexible Slip-on Flat Lady Casual Sneakers Walking Shoes Solid , Women's Propet Women's Swift Elegant Shape Athletic ShoesWomen's CC RESORTS CARRIE LIGHT GREY Beautiful Flats , AC61 SUSIMODA shoes brown leather women sneakersASICS Women's GEL-Excite 4 Running Shoe , New Balance WR2102TP: Women's Taupe Traverse Leather SandalsCatahoula Leopard Dog Running Shoes For Women-3D Print-Free ShippingNike 599409 Women's Air Max Thea Shoes $90 Running Sportswear Casual SneakersASICS GEL KINSEI 2 TN799 Sz 7.5 EURO SIZE 39 Pink Silver Atheltic SNEAKERS j609Converse Chuck Taylor All Star Women's Raspberry Canvas Ox 132298F 6 8 9 10Women's New Balance 574 SPORT Suede Shoes Wool Lined Blue Pink White Size 7.5 , Skechers Microburst It's My Life 23310/BKW Black White Brand New In BoxKeds Women's Triple Kick Leather White Sneaker WH57310 , Asics Gel Kayano 25 Womens Running Shoes 7 Wide New , MBT Lifestyle By Swiss Masai Red Shoes
"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."