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.Spring&Summer Woman Shoes Ankle Straps Buckle Flats Pointed Toe Shoes , New Worthington Gingham Slide Sandels SIZE 10 M , Cole Haan Womens Deck Boat Shoes Melon Red Leather Sz 8.5 B $150 RetailCROCS Lina Graphic Women's Leopard/Oyster Standard Fit Flat Shoes Size 6 NEW , Merona Woman's Flats Boat Shoes Blue And White Leather Moccasins Size 6.5 M , SAS VTO Tripad Comfort Shoes Black women's 8Basic Editions SHOES WOMENS SIZE 8 MEasy Spirit Kellye Shoes 10 WW , Tommy Hilfiger Womens Frank8 Suede Closed Toe Mules Navy Size 7.5 ioHY , crocs Womens Lina Luxe Ballet Flat, Black/Plum, 8 M US , NEW STAR Women Outdoor Sneakers Fashion Comfortable White Shoes 4556 g_C , Fashion women winter fur Plus size soft leather loafer flats lovely shoes KoreaSANUK ON THE PROWL METALLIC GIRAFFE HEMP SIDEWALK SURFER SHOES, US 6/ ~NWT , NIKE NEW WITH DEFECTS Stamina Women size 5.5 685068409288 , EUC-ASICS Women's 1150 Gel Running Shoes Style T065N-0136 size 9.5 , Womens Super High Heel Platform Wedges Sport Sandals Strappy Ankle Boots PumpsSuperga Womens 2750 Cotlinu Canvas Low Top Fashion Sneakers Shoes BHFO 3406 , Skechers Performance Womens Go 4-Airy Walking Shoe- Select SZ/Color.J Slides Women's Rosa Fashion Sneaker, Black/Multi, 8 US/US Size Conversion M USREEBOK CLASSIC Brown Athletic Shoes Womens Size 7.5Converse ALL STAR Chuck Taylor OX Black White Red Navy CANVAS Men Women Unisex , Ryka Lily White Walking Shoe Slip on Comfort Casual Sneakers Women's US 8M BOXPuma Womens Suede Classic Sneaker Shoe Grey & Purple Size 10 M US , NEW BALANCE 860 v3 Womens 9 M Black Pink RUNNING SNEAKERS SHOES , nike pegasus 28 Running Shoes Women Size 7 Great ConditionADIDAS ZX FLUX W "TOKYO LIGHTS" [B25834] US WOMENS SZ 10 , Wmns DC (Navy White) Chelsea TX SE Shoes , Lacoste Pirle 217 1 G White / Black US Size 6 - FREE SHIPPING - BRAND NEWNew Balance WR996WE D Wide Blue White Women Casual Shoes Sneakers WR996WEDVasque Women's Breeze 2.0 Castlerock/Tender Shoots Hiking Shoes 9.5M ,
"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."