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.SAM & LIBBY Womans Brown Animal Print Flats Size 7.5CLARKS Women's "Bendables Sixty Delta" Brown Leather Loafers Size 7NEW SOFTWALK MARSEILLE BLACK TUMBLED LEATHER SLIP ON WEDGE SHOES 6 MEtienne Aigner Grey Women's Loafers Loafer Black Flats Moccasins Shoes - SZ 7.5EUROSOFT SOOKIE STRAPPY FLAT FB-02-08-01 BLACK SHOES WOMENS SZ 9.5 NEWWolky - US 6 - 6.5 / Brown Brushed Leather Suede , Rialto- Viva Clogs, Women's Size 7.5 M, NavySteve Madden Womens Cannon Ballet Flats - Black Nubuck Size US 8.5 NWOBClarks Originals 78135 Faraway Fell Taupe Leather Mary Jane Shoes Size 8 , Tod's Black Suede/Patent Leather Loafers/Flats/Shoes Size 35.5Kelsi Dagger Brooklyn Womens Gwen Tassel Loafers Shoes Latte Size 8.5 New , Women's Minnetonka 3 Layer Fringe boots Size 7 , Cole Haan Collection Woman’s Black Woven Leather Ballet Flats Shoes Italy Sz 9BZee Alexis Women's Sammi Woven Mary Jane Shoe Mosaic Multi 10 MDr Comfort Breeze Sandal Black Leather Fisherman Shoe Womens SIZE 6.5W (WIDE , Women's Puma Navy Blue Leather Sneakers 7MWomen's JANA Derby 23702 Noir Ideal Gift For All Occasions Athletic Shoes , Women's Jack Rogers Baldwin Sneaker Cheap Athletic Shoes , Reebok Women Athletic Shoes Size 6.5 Euro 37 White Blue Beige Easy Tone , Adidas Originals Sneakers Shoes SZ 7.5 /Nike Multicourt V Women's Size 9.5 Athletic Shoes EUC FREE USA SHIPPINGSaucony Shadow Genesis Women's Shoes Size 5 , Etnies Senix D Mid Stone Women's Size 11 US BMX DC Skate Shoes Sneakers ShamrockWomen's Bright Yellow Nike Cortez Sneakers Size 12 Worn Once Free ShippingVionic (335 Fyn) Orthaheel Crosstraining Running Shoes size 6 M Blue/Pink New! , Mizuno wave inspire 11 size 7.5 running walkingAsics Gel-Resolution 6 2016 London Special Edition Women's Tennis Shoes SZ 11 , La Sportiva Womens Bushido Athletic Outdoor Trail Running Shoes US 9Sam Edelman Womens Baylee Blush/Dusty Rose Fashion Sneaker Size 10 (27885) , Columbia Yama OutDry Waterproof Hiking Trail Shoes Womens 8 / 39 Mud Daybreak ,
"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."