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.Minnetonka Tunderbird II - Brown US 6 , NWT Sanuk Willow Pillow Furry/Knit Flats Slip On Slipper Hard Sole Shoes Women 6 , Marc Fisher Slip-on Flats w/Jewel Accents - Cadassi Silver (1677) Size 6.5MBASS Celeste Brown Suede Leather Ladies 7.5M Slip-on Clogs Mules Cork Slides , Cougar Womens Black Waterproof Rain Shoes Sneakers 8 Medium (B,M) BHFO 0900��� BALLERINES MOCASSINS SUEDINE H&M CHAUSSURES NEUVES H&M TAILLE 38��� , Vintage Woman's Size 8M Leather Oxford Moccasin Hush Puppies Shoes , Brown Leather NAOT "PRIMOSE" Mary Jane Flats 37/6 MMNP620174SJ BROWN LMPF60 Women's Shoes Size 7 M Suede Slip On MephistoUS WOMEN KHUSSA SHOES PAKISTANI JUTTI BRIDAL SHOES INDIAN SARE KURTI SHOES DD734 , Cole Haan Country Black Woven Leather Shoes Women's Size US 9.5 AA Loafers , Cobb Hill by Rockport Women's Deidre Leather Slip On, BarkLotus Ladies Cream Snakeskin Leather 70s Retro Strappy Sandals /38.5 , KELSI DAGGER BROOKLYN Abbi Loafer Rosso Red Nubuck Pointed Toe Low Wedge , Asics Gel -1140v Women’s Volleyball Court Shoes 7.5RYKA Womens Sz 11 W Black Slip On Zip Up Shoe Water Resistant Duck Shoes 11 Wide , Saucony Redeemer Running Shoes-Women's size 8.5 Silver , Merrell Siren Sport Trail Hiking Shoes Khaki Brown Vibram Womens 7 US 37.5 EURWomens Brooks Adrenaline GTS 17 Athletic Running Cross Training Shoes Sz 8 WideWomen’s White / Purple Asics Gel Conteno Athletic Running Shoes Size 6 , Adidas Women's Alphabounce Rc Running Shoe , Women's Cole Haan W07303 GrandPro Perforated Sneakers Shoes 8.5B Navy BlueFuntasma Women's Love 270 Yellow Patent , Reebok Women's High Top Red Shoes Aspire 2Vans Womens Old Skool Sneakers Embossed Sidewall Blanc de Blanc White Size 10 Ne , Nike presto (GS) youth running trainers 833875 441 sneakers shoes , New Balance Womens 860V8 NYC Marathon 2017 Running Shoes Size 5.5 KJ860NBY , Womens Saucony Kinvara 6 Running Shoes run walk Size 8 cleaned , Clarks Glove Glitter Comfort Sneakers, Black/White, 7.5 US / 38 EU , New Balance Womens - Gray Running Shoes Size 5 (361560)
"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."