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.EUC BORN WOMENS BLACK SUEDE CLOGS SHOES SIZE 9 40.5813 Tory Burch Reva Black/Silver Leather Scrunch Collar Flats Women's Size 7.5 M , NEW BOBS from Skechers Women's Highlights Flexpadrille Wedge Taupe Pick A Size , BARE TRAPS ELLINA WOMENS BLACK LEATHER SLIP ON CLOGS MULES SIZE 6MEcco Women's Shoes Clogs Flats US 6-6.5 Black Leather , Dr. Scholl's Frankie Faux Leather Ballet Flats, Women's - Size 7.5 M, Black , TOMMY HILFIGER Women Casual Penny Loafers Size 8 Red Leather/Synthetic , NEW WOMENS ASHRO ELECTRIC BLUE LUCITE HEELS SHOES SIZE 7M 7 MBOC Born Concepts Womens Canvas Shoes Beige Clogs Mules Low Heel Sz 9 MSkechers Women's Go Vulc Ventura Fashion Walking Sneakers Shoes - Red & Blue , Dansko Brown Leather Clogs Shoes Sz 38/L7.5-8Boc Born Concept Brown Leather Clogs Size 9 Buckle Women's Mules Slip On Shoes , Womens Melissa Vivienne Westwood Ultragirl Shoes Size 10 , Nina Klaire Flats-Women's size 8 M SteelMerrell Encore Breeze 3 Casual Shoes, Women's Size 10, BlackWittner Brand Shimmery Cream Davin Leather Ballet Flats Size 39 NEWEUC MERRELL Women’s Casual Dress Mary Jane’s Size 9.5 Color Brown SuedeB35 Hint Slip-On Sneakers 432, White, 8.5 US , Cole Haan Navy Velvet Women's Shoes Marlee Skimmer Loafers Flats 6 B $180 , New Keen Womens Terradora Mid Waterproof Athletic Trail Hiking Shoes Size 6 , Saucony Guide 10 Womens US Size 7 Running Everun Sneakers Shoes Light PurpleBeacon Shoes Women's Dandy SneakerSkechers Women's Bright Idea - Fleet Footed Casual Shoe , Men's Shoes Slippers Reino Home Shoes Strong Resistance To Heat And Hard Wearing SlippersAdidas Pureboost X Womens Size 8 Running Shoe , Brooks Launch 4 Running Shoes Black/Pink/Purple Women's US 9 (H2,27) , MERRELL HIKING TRAIL SHOES WOMENS 8 SUEDE FREE SHIPNike Women's Eclipse II ( 386199-017 ) 5.5USNEW Saucony Grid Web Memory Foam Running Shoe s15291-4 Teal Size 7Puma Fierce Evoknit - Black - Womens
"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."