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.Black Leather Size 9 M Bass Womens Ellen Loafer Shoe Silver Ring Accent , Circus By Sam Edelman Women's Lena Black Espradrille Flat 6M , BCBG Ballet Flats Shoes Sz 7 Womens Camouflage Faux Fur Flower Loafers BrownU.S. Polo Assn.Women's Juno Fashion Sneaker Black *Mismate* Left 5.5 / Right 6 , NIB Lady Bright Camel Tassel-accent Mules Shoes 8 MRockport Maroon Suede Mary Jane Comfort Shoes Kinetic Air Circulation Sz: 6.5WNine West Women's Unah Leather Pointed Toe Flat Natural Size 9.0ANNE KLEIN PLURAL BLUE MULTI SUEDE FLAT WOMENS SIZE 6 MCorky's Women's Joann Slip On (Blue Multi) , Calvin Klein Womens Shannin Loafer Flat- Pick SZ/Color.KLOGS CLOGS NATALIE WOMEN'S DISPLAY MODEL SHOES GEO PAISLEY 7.5 MAsh Jordy White Leather Women's Slip On Platform Oxford Sneakers Size 41 / US 11 , Via Spiga Size 5.5 M Lilac Copper Leather Flats New Womens Shoes , NWT Women's Champion Women's AthleticShoes Size 7-1/2 MSteve Madden Loafers Size 7.5 Tassel Leather Flats Career Slip On Brown ShoesNEW Kenneth Cole NY Women's Kalvin Hi Top Ankle Sneakers Black Comfort PICK SIZENaturalizer Harken Casual Shoes, Brown, Leather, Womens US Size 8.5 , NEW BALANCE 993 WR993GL CLASSICS RUNNING SHOES WOMEN'S 8.5 / /HOT women's sports sneakers leisure athletic running slip on jogging shoes NEWPleaser Pink Label Women's Fab 428 T-Strap Red-Black Patent T Straps , Twisted X Boots Women's and man's :)? ?WDMS008 Driving MocNike Womens Nike Dunk Hi Ease White Black lot 896187 101 Womens Size 5.5nike air max 1 (GS) running trainers 653653 005 sneakers shoesNike 833801 400 Womens Cortez Ultra BR Training Running Shoes Sneakers , Mizuno Wave Creation 19 Athletic Shoes - Women's Size 8, Black/Teal/PinkKeen Newport 8 Black/Teal/Mint Women's US 7 (N3,3) , Original Vans Classic Slip On VN-0EYETZH Casual WOMEN , Easy Spirit Motion Anti-Gravity White Leather Oxford Walking Shoes Womens Sz 6 , WOMEN'S ROCKPORT COMFORT DMX, BROWN LOAFERS SHOES 10 1/2 M NON SKID , NWOB Diadora WOMEN'S Aeon Green Ash ATHLETIC Running SHOES Sneakers Size 7
"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."