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.Cole Haan Sz 6 1/2 Women shoesDREAMS WOMEN'S ROUND BALLET FLATS BLACK SYNTHETIC IMPORTED US SIZE 7 MEDIUMTIGERBEAR REPUBLIK OLIVE SOAPBOX NIB 6M SNEAKERS SHOES HIGH TOP PATCHES CANVASCindy Says Womens Shoes Sz 7 US Flats Black Dress Sandals Heels Casual , REGENT-27X-00 WOMEN STUDDED MULE QUPID WHT PU , NIB Banana Republic TONYA Sandals Size 5.5 BLACKCROCS Feat Clogs, Women's size 7 Men’s size 5 Walnut. , CLARKS BROWN LEATHER SLIP ON LOAFERS WALKING SHOES SIZE 9 M , BORN “Sitton” Multi-Color Striped Fabric Leather/Jute Loafer Flats 11 NewAerosoles A2 Have Fun Womens Gray Blue Nylon Slide Flat Mule Shoe NWOB-Size 10M , Madlove Womans Sz 6 Canvas Beach Boat Shoes Slip On**Easy Street Elliot Mules - Women's Size 9 M, Pewter CrocELIE TAHARI Black Sequin SOFT BALLET FLATS Slip On Sparkling Womens Shoes 10 , Rieker Women's Slip-ons Low shoes, Sneakers trainers, black L0551 NEWECCO / MADE IN DENMARK / SUPERB CLOG IN BROWN / sz: 38 / EXCELLENT , Authentic Prada Italy two tones w/ silver buckle shoes Size 36 or US6Bellofatto Red Snakeskin Ballet Flat Size 7 EUC , Women's REEBOK DUAL RIDE Z Athletic Running Shoes M44668 Size 6.5 M USTOM'S WOVEN PLAID PALMERA SLIP ON SNEAKER US7/UK5/Women Casual shoes Students Rose High Platform Wedge heels Slipper Mules Shoes , Nike Free 4.0 Womens Sz 11 Running Shoes Hot Pink , Sperry Top-Sider Paul Sperry Women's Sayel Away Sport Sneakers Shoes Black , MBT 400092-06 Lami White Mesh Rocker Mary Jane Walking Sneakers Women's US 9 , ASICS GEL KAYANO 21 T4H7N BLUE PINK WHITE RUNNING SHOES US WOMENS SIZE 9.5 , Converse Womens Chuck Taylor All Stars Size 7M Black Jeans Triple Zip Sneakers , Merrell Womens 10 M 41 Run Bare Access Ultra Running Shoes Monument Tanga J01648 , Zero Drop Vibram Women's shoes VI-B Fitness and Yoga Shoe Trek Outsole washableRhinestones Women Strappy Creepers Athletic Sneaker Casual Shoes Color StitchingNIKE ZOOM VOMERO 11 Gray Blue Purple Womens 6 M 818100-405 Running Shoes Sneaker , K-Swiss Women's Sneakers / Tennis Shoes Tan Size 9 EUC ,
"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."