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.Mudd Wedge Sandals Flats Peep Toe Shoes Tan Plaid with Bow Size 8.5 ADORABLE , SAS TriPad Comfort---162351---Ivory Penny Loafer w/ Apron Toe---10 N , COLE HAAN Country Women's Loafers Green Suede Slip On Moc Toe Shoes Size 7.5BLadies Cole Haan Black Nubuck Slip-Ons 8 Med *2 TRAIN AUTISM SERVICE DOG 4 SON*New Bucketfeet Slip On Canvas Pineappleade Shoes Sneaker Size 6 W/Artists CardDANSKO Brown Leather Loafer Heels Shoes Women's 37 6.5Easy Spirit Travelport 17 Navy M Suede Womens Clogs Size 9MEastland Womens Cora Slip-on Wedge- Pick SZ/Color.Gentle Souls Split Toe Loafer Size 8.5 Antique Pewter Metallic Slip On ShoesNEW BALANCE 750 v2 Black Peach Running Training Shoes Sneakers Women's Size 9.5 , Nike Dart IV Women's Athletic Running Shoes Size 9 Brown Pewter 313801-241Converse Hi Tops Trainers Sneakers Vintage Unisex Purple US 7.5Nike City Court Shoes 488136-101 Women Size 9.5 , HI-TEC Womens Equilibriobijoulowi-W Black/ForgetMeNot Walking Shoes Size 11WOMENS NIKE DUAL FUSION LITE RUNNING GYM SHOES WORN SIZE 7.5 7 1/2 , Naturalizer Harken Casual Shoes, Brown, Leather, Womens US Size 8.5SKECHERS women's shoes black orange pink yellow slide wedge sandals SIZE 9KENNETH COLE REACTION WHITE LEATHER BEIGE SUEDE WOMEN GOLF SHOES SZ 7 , Clarks Dowling Pearl Cloud steppers size 9 Women's Shoes Missing Insoles , Women's Reebok Classic Harman Run Sneaker Online Sale Athletic ShoesPUMA Women's Ignite Flash Evoknit Wn Sneaker - Choose SZ/ColorNew Balance Running Pace V2 Size 6 WPACEWP2 Women's Vazee Blue / Pink RP $110 , New Balance W530CUA - Women's W530 Classic Running Fashion Sneaker , Nike Air Max Jewell Women's Running Shoes (Size 7) Light Bone 896194-002ASICS Gel Kayano 21 Purple/Silver/Green Running Shoes T4H7N Women’s Sz 11 , Women's New Balance WXAGLDG2 Training Shoes - Navy/White - NIB!Reef Rover Low Sneakers - Women' Size 5, WhiteWomens skechers shoes size 9 (new with box)Paul Green Munchen Fashion Sneaker Size 7 US 4.5 UK Womens Brown Athletic Shoe , New in box Womens Montrail Rogue Fly Hiking Trail running shoe Harbor 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."