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.Soft Style Women's Angel Lo Platinum Gold Flat 7XW , Rockport Adidas Gold Ballet Flats Sz 5.5 Womens Metallic Leather Shoe Adiprene , Women's Shoes Bamboo Standouts 30 Round Toe Ballet Flats Blue Denim *New* , E Spirit Black 9M Diamond ES Textile Upper Shoe , Gap Womens Cork Cap Toe Ballet Flats Silver Size 7 , Sidekicks Women's Tan Vinyl Foldable Ballerina Flats | Size XL ( 10 - 11 )Predictions brand women's pink flats, satin fabric uppers, 7M, 3/4 in. heelSAS Softie Tassel & Kiltie LOAFERS Moccasins Womens Size 6 M NAVY Tripad ComfortWomen's Size 7.5M CROFT & BARROW Gray & Black Slip on Ballet Flats, Silver & Bow , Ladies Womens Flat Sandals Buckle Strappy Cut Out Studded Gladiator Summer Shoes , Sanuk Pick Pocket Knitster Black Shoes Womens Size 6 1017935 Slip-on NWT , SANUK KATS MEOW TEXT Prints Black / White SLIP ON Flats Sneakers WOMEN'S SHOES 7 , Sperry Top Sider 61248 Cherubfish Mariner Stripe Boat Shoes Women's 9 M , Cinch Casual Women's Embroidered Tan Leather Shoes CCW3019 CLOSE OUT SALE!! , Jeffrey Campbell CADEAU Flats Moss Suede Pointed Toe Cut-out Design MSRP $160Women's New Balance White, Gray, & Blue WX409WL Shoes Size 9 BK-Swiss Court Pro II T CMF Women's Sneaker Size 8 Rainbow/ White Tennis Shoes , Minnetonka Tyler Trapper Moccasin Slippers - Men's Size 9M, Toffee 532 , DVS Women's Cinch LT WOS Skate Shoe, Grey Knit, 6 Medium USNew Balance 574 Women's Size US 6.5 Gray Fashion Sneaker , Musse & Cloud Womens Anaeh Brown Booties Shoes 5 Medium (B,M) 36 BHFO 7464 , VANS BLACK WHITE PLAID WOMEN'S SIZE 11 SNEAKERS NEW , Womens Nike Lunarepic Low Flyknit Size 6 (843765 100) No Box , Eileen Fisher Clifton 3 Sneaker - Women's Size 9 - Gray , SAUCONY FAST TWITCH SUPER LIGHT RUNNING SHOES WOMEN'S 9 M RTL $90ASICS Women's Gel-Nimbus 18 Athletic Shoes Sz 8 Gray Neon Yellow Blue T650NBrooks Ariel Gray White Running Sneakers 9 M Women , Fila Womens Memory Workshift Training Shoe- Pick SZ/Color. , JOIE Kidmore Rose Gold Leather Slip On Sneakers Shoes $220 NEW 38 8 , ASICS Womens - Blue Running Shoes Size 8.5 (361755)
"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."