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 Women's Light Brown Loafer Slip On Driving Moc Shoes - US 8.5 , GREAT CONDITION! CLARKS SLIP ON SHOES CLOGS 2.5" HEEL- BROWN-7M , Diane B. Milano Women Shoes Slip-On Leather White Quilted Pointed Toes Sz 39/8USBirki's Germany Made Maria Womens 7 38 Brown Leather Clogs Slides Mules Shoes jq , Not Rated Womens Trenoly Mesh Gray Slip-On Shoes 8.5 Medium (B,M) BHFO 8162Women Ballet Flat Party Glitter Shoes Fashion Cut-Out Design Brilliant New StyleEDGE DESIGN - Women's Bronze Metallic Leather Moccasins - Loafer Shoe - NEWEUC Womens BORN Black Leather, Shoe, Mary Jane, size 8.5DOLCE VITA WOMEN'S SOLOMAN FLAT, COGNAC NUBUCK, US SIZE 8.5, MEDIUM, NEW W/O BOXPropet Womens 6.5 Taupe Leather Shock Absorber Walking Shoes Sport CasualTrotters Women's Jenkins Flat, Black, Size 8.0 , Skechers BOBS from Women's Bobs Plush-Wag Town Flat Black/Multi 9 M US , Clarks Artisan wedge w/ ankle strap brown leather cut out embroidered accents 9Bernie mev. Catwalk Black US 6.5-7 M57 , Mephisto City Hiker Brown Suede Walking Shoes Women's 9.5 Men's 7.5 , Saucony Womens S30003-1 Gray Running Shoes Size 5 (275162)NWT Women's FILA BLACK LEATHER RUNNING ATHLETIC SHOES, Size 6.5, SLIP RESISTANT , Nike Revolution 2 Running Training Gym Shoes Colorful Sz 7.5 38.5 Pretty 554900 , Simple Brand Sz 9.5 M Tan Brown Suede Leather Comfort Walking Shoes SneakersChampion Girls' Blue Coral Girls' Gusto Cross Trainer 2.5 Regular , Skechers Bikers Roamer CHOCOLATE Brown Leather Memory Foam Slip On Shoes Sz 7.5 , Women's UNDERARMOUR WOMENS SHOES SIZE 8 Louis, Elaborate Athletic ShoesMen's Shoes Slippers Glerups Boot Slipper Red 37.0 Customers First Slippers , Women's Leather Slide Shoes Sandals Big Clearance Sale Flats , Reebok Size 7.5 Wide Running Sneakers New WomensValentine's Day Special-Rottweiler Print Slip Ons For Women-Free Shipping , VANS SK8 Hi Slim Zip (Plaid Flannel) True White Black High Top WOMEN'S 10ASICS Womens - White Walking Shoes Size 6 (361574)New Balance Women 696SRW Sneakers, White/ Metallic SilverReebok Women's CL Lthr Satin Sneaker ,
"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."