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.Rocket Dog Women's Malt Coast Fabric Pointed Toe Flat, Cinnamon, Size 8.0 , AGL Chain Belt Ballet Flats Black Nappa Leather Cap Toe size 36.5 6.5 , Qupid Women's Size 6 Loafer Black Faux Leather Twisted Rose Bow Toe Slip On Mule , Vince Camuto Womens Flats Size 7.5 Black Metallic Pointed Toe NEW , Mephisto Shoes Women's Air Jet Loafers Black Leather Mocs Clogs Sz 5.5 MCHACO PEDSHED 7 CHOCOLATE BROWN CLOGS $125 , SAS Roamer Mary Jane Nubuck Leather Comfort Walking Moccasin Shoes Size 9 WIDE , Clarks Women's Dark Tan Prestlet Grove Leather Clog Mule Shoes Ret $95 NewMarc by Marc Jacobs Women's Pink Black Heart Print Ballet Flat Shoe Size 8.5 , SPERRY Top Sider Women Beige And Black Patent Leather Penny Loafer Flats Size 5 , Steve Madden Women's Lancer Fashion Sneaker Black Size 10.0 kvA8 , Mix No 6 Womens Vantage Closed Toe Ballet Flats Black Size 6.0 QR9i , Kenneth Cole Reaction Womens Put On Bold LK Closed Toe Black/Leopard Size 5.5 , Alegria Petal Blue Multi Rave on the Nile Leather Slip on Comfort Shoe NEW , NEW Orthaheel Sara Women's Brown Leather/side Mary Jane Flats Shoe sz.10 , Cole Haan Gold Slip On Flats Womens SZ 7 , Skechers Show Stopper Women's White Sneaker 9M , PAIR OF WOMENS SIZE 8.5 TAN AND BROWN RED BY MAROSOKO CANVAS SNEAKERSShoes Black 6.5 Ballet Style Slipon Shoes Self Esteem Kristi size 6.5 New , Orthofeet Gel Red Leather Walking Casual Mary Jane Womens 12 M Shoes Comfort EUC , 2014 Soft Warm Comfy Corduroy Men Winter Slippers Casual Out/Indoor Slip On Shoe , Nike Air Predecessor Casual Sneakers, Grey/Pink, Women's US 9.5 , Salomon Techamphibian 3-W Performance Boat Shoes Womens Size 6.5 Shrew , New Women's Skechers Burst Equinox Walking Athletic Sneaker Shoe 12431 BKTQ 131DFRYE Women's Melanie Mule Sneaker Cognac Size 6.5Keen Presidio Mary Jane Cognac Leather Women's Shoes Size 11 W , Propet Women Travel Walker II W3239 - Silver Light Weight SneakerNew Balance Womens Ww1865vpl Purple Walking Shoes Size 9.5 (2E) (21504) , Skechers Flex Appeal 2.0 Change Up up Womens- Choose SZ/Color.Propet W3851 Wash & Wear Slip-On Sneakers - Women's Size 8.5W, Black
"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."