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.Women's TOM's Suede Slip On Shoes Sz 12M Size $64- , Rieker Antistress Womens Loafers Sz 4.5 Celia Brown Leather Comfort Shoes , Cole Haan Silver Peep Toe Criss Cross Flats Shoes, Size 6.5TUK flats 6 bear black plaid XSperry Pattern Brown Shoes Size 7Dark Navy Blue Flats With Strap Size 10 , Merrell Womens Shoes Plaza Moc Dark Brown Suede Leather Slip On Flats S03D1Lands’ End Suede Leather Black Round Closed Toe Comfort Flat Shoe Women’s Sz 97818030 LSP30 Women's Shoes Size 7 M Bronze Leather Slip on Johnston & Murphy , Judith Ripka Black Leather Snake Emboss Captoe Alberta Ballet Flats 6 NEW , Brinley Co Women's Laci Ballet Flat, Rose Gold, 7.5 Regular US , Earth Origins Evelyn Women Loafer Navy Grained Leather/Silk Pig Suede Size 7MSerra women's 9 sneakers athletic shoes NIB new , 1511 Filling Pieces W Ghost Tone Altrosa Sand Suede Low Top Sneakers Women Sz 40 , Easy Spirit Active Women's AP1 Red Suede Casual Sneakers Shoes Size 8.5 M NEW , Minnetonka Women's Pacific Slip-On Shoes - 670P , NEW Nike Women's AIR COMMIT Basketball Shoes , size 9.5 , Without boxSkechers Shape Ups SN11809 Women Sz 7 Blue White Rocker Toning Athletic Shoe AV1Dr SCHOLL'S WOMEN'S ATHLETIC SNEAKERS s 6 Genuine Leather FRIDA BLACKKim & Zozi Glitter Hi Women's Hi Top Shoe - Women's Size 8, Multi-ColorConverse CTAS Low Sneaker, Women's Size 6.5, Black , Harley Davidson Womens Hi Top Sneakers JADE Black Denim , DS NEW Wmns Puma Rihanna Ri Ri Bow Creeper Sandal Pink sz 6 Free Ship , New Balance KA520NWY W Wide Black White Suede Kids Preschool Shoes KA520NWYW , REEBOK Classic Free Style HI Women's Basketball Sneakers White 70 Sz6-8 L , VANS Sk8 Hi Reissue (Denim C&L) Periscope/Dachshund MEN'S 7 WOMEN'S 8.5Dr. Comfort Women's Flex-OA AMY Black Diabetic Athletic Shoe Size 7 M/W New W/O , WMNS NIKE DUNK LOW 309324-144 WHITE/MID NAVY-DEEP RED WMN'S SIZE 11.5 MEN'S 10H , AETREX Z581 Zoom Runner White Blue Orthotic Sneakers Women's 7.5 Medium , Nike Women Athletic SNEAKERS Shoes Size 9 Blue
"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."