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.Lucky Brand Women's LK-Fintleyy Black Pewter Leather Flats - Sz 9.5M STYLISH!Massimo Baldi shoes womens size 6.5B black suede leather ballet flats ItalyWomen's Alpargata Huarache MADE IN MEXICO , Romano Women's Brown Leather Brazilian Clogs Size 8.5 , objact-20 New Slip On Casual Round Pointed Cap Toe Women Flats Shoes Nude 7.5 , NWT $65 Propet Womens Morgan CIGAR Microsuede Slipper Shoes 6.5 Medium (B,M) , Minnetonka Moccasins Britt Womens 10 Pink Suede Slippers Shoes Faux Fur 40325Dr. Scholl's Madison Casual Slip On Shoes - Women's Size 9 M, GrayWomen's Josef Seibel Black Leather Loafers Size 6.5 (US)Dr Martens Womens USA 6 Oxford Shoes Cap Toe 8651 Brown Leather - S1 , Clarks Women's Artisan Felicia Emma Strap On Leather Shoes Style 26102677 Olive , Womens Rivet Decor Creepers Loafers Slip on Wedge Hidden Heels Shoes Round Toe L , Vans Off the Wall Women's Surf Palisades Vulc Striped Blue Shoes Size 6.5 M USVIBRAM Fivefingers Barefoot Gray Running Water Walking Shoes Woman’s Sz 36 US 6Skechers Go walk Cherish Walking Shoes-Women's size 10 W GreyMen's Realtree Xtra Camo Clog Slippers - Size 11REEBOK PRINCESS 1475 WHITE WHITE Core Classic WOMEN Size 12Clarks Collections Women's Sneakers Size 8M Black Pink , Easy Spirit Quade Slip On Sneaker - Women's Size 8.5, WhiteWomen's? Skechers 31397/BLK Bobs B Loved-Casual Party?Tennis Shoes Black , Sunsports Shoes - Knitted breathable Sneakers - GroveNike Free RN Motion Flyknit 2017 Women's Running Shoes Gray Size 8.5 880846 002 , NIKE OUTBREAK HIGH SNEAKERS WOMEN SHOES ORANGE/YELLOW 318635-701 SIZE 6 NEW , New Women's New Balance W770 Sneakers Running Shoes , Saucony Shadow Genesis Women's Shoes Size 5VANS Rata Vulc SF Dress Blues/Gum Slip On Skate Shoes WOMEN'S Size 8.5 , Vibram FiveFingers W346 Bikila Outdoor Shoes Womens Size 8.5-9New Balance Women's Fresh Foam Zante Summer Utility Shoes Purple , Gabor Jollys Woman's European Walking Shoes Leather High Quality Size 37 US 6$75 SUPERGA Red Blue SIlver Check METALIC MESH Sneakers Shoes NEW COLLECTION
"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."