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.NIB Eddie Bauer MIGHT women's slip on deck boat loafer Memory Foam Red Black NEWA35 Aleaa Ballet Flats 831, Black Patent, 7 USSam Edelman Women's Baylee Blush/Rose/Shmr Sue/Veluto SUEDE SZ 8.0 M NEW D6785*111317sho -- Dr. Scholl's Woman's Shoes Sz 11 Gel Pak Black Shoes Leather BootSAS Tripad Comfort Roamer Mary Jane Velcro Shoes Black Leather Women Size 10 S , JOSEF SEIBEL women's shoes, heels, size 40, Brown leather. Mint condition , Sebastian NWOB Beige Leather Stud Bow Accent Ballet Flat Shoe Size 37 7 , Dr. Scholl's Bradyn Casual Slip On Shoes - Women's Size 10 M, BlackSkechers Flex Appeal Align Casual Shoes, Light Grey/Pink, Women's US 8 , New Balance All Terrain Shoes Size 8.5B Gray/Pink Trim WT461RP , Merrell Relay Tour Green Womens Size 5.5 Hiking Camping Backpacking , BOBS from Skechers Women's Highlights-Jewel Rock Ballet Flat , Women's Minnetonka Me To We Maasai Moc - Taupe - Width: med - FlatsCorkys Womens Liz Fashion Woven Flats Shoes , Nike Lunaracer+ 3 Shoe Size 9.5 Womens 554683 830 , Converse All Star Grey Gold Studded Collar 540366C Canvas SneakersSKECHERS WOMEN'S SHAPE UPS-11809-Running Training Toning Black/White-Size 9.5Nike Flex Experience Rn 4 Women's Running Shoes Size 7 Aqua GreenVANS Womens Size 9 Purple Shoes Low Casual Skate Skateboarding , Puma Roma Womens Purple Sneaker 9.5 , Asics T075N Gel-Kahana 5 Womens Running Shoes White Pink Gray Silver Size 8Athletech Snickers for girls size 3 1/2 , NEW Navy Red & Silver FILA VECTOR Shoes Sz 7.5 ***FREE SHIPPING*** , Merrell Around Town Sunvue Woven Women's Size 7 Black 25%OFFNike W Roshe LD - 1000 Shoes Blue/White WMNS SZ 9.5Reebok WOMEN'S PT Prime Runner Athletic Shoes Size 7.5 NEW with box USA SellerAdidas Pink Black White Womens Running Shoes Trainers Sneakers sz 7 Med , Vans SK8 Hi Slim Zip Valentines Heart Pink White Beet Canvas Shoe Women Size 9.5 , Reebok BD1974 Womens Furylite Loom Fashion Sneaker- Choose SZ/Color.NEW BALANCE Women NBJ Ss10 Brown Chocolate Shoes size 6.5 Sneakers W364LDB
"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."