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.M18 Opening Ceremony Charly Navy Suede Slip On Shoe Women's Sz 39 M , Aerosoles Womens Gallerina Black Woven Leather Mary Jane Moccasin Shoe-Size 7.5MVince Camuto Womens Dalmi3 Black Flat Espadrilles Shoes 6 Medium (B,M) BHFO 3183 , Steve Madden Womens Hydes B/W Mule Loafer Slides Shoes 7 Medium (B,M) BHFO 2222 , Born "Marti" Women's Sz 8 / 39 Black Suede Ballet Flat Shoes Bow Round Slip OnVintage Gyllene Gripen shoes Suede Brown 12M Shoes Women's MoccasinSkechers Womens Leather Mary Janes NWOB Size 6M SR2 , Sperry Top Sider- Darlington Women's High Heel Loafers , NEW!, sz. 7 M , Crocs Sarah Clog Espresso Womens, SIZE 7 - NWT - Free Shipping $50 , Kelly & Katie Womens Cigola Pointed Toe Loafers light pink Size 9.0 dJjtWomen's Clarks Bendables Mary Jane Style Brown Leather Shoes Size 8.5 strapSoftwalk Brown Padded Insole Comfort Shoes 8.5N , Anne Klein Womens Noris Closed Toe Loafers, Tan, Size 9.5Blue Texture Sperry Gold Cup A/O Honeycomb Boat Shoes, Women's US 5, NEWSale $20 Bensimon SuedeTennis Shoes Color Khaki U.S. Size 6Fashion Women Running Shoes Outdoor Breathable Sports Sneakers Walking Shoes , DC Women's Villainess TX Flat,Pewter,5 M USNIB New Kenneth Cole New York Kiel Leather Gray Sneakers Shoes Grey US8 Womens , GENUINE ALPACA / LAMB WOOL MEN SLIPPERS BOOTS NEW , Easy Spirit Traveltime Clogs Slip On Bronze Metallic Women's 7 Bonus Puma 7.5 , LL Bean Women's Walking Shoes SZ 8 Little Wear , Merrell Pulse 2 Womens Sneakers Hiking Shoes Size 7 , Asics Womens sz 9M GT-1000 Jogging Running Training Athletic shoes Aqua/BlueLucky Brand Lotuss 3 Silver Womens Shoes Size 7.5 M Fashion Sneakers MSRP $99 , WOMENS REEBOK CLUB C 85 DIAMOND in colors WHITE / GUM SIZE 6.5MBT Shuguli GTX Black Leather Gore-Tex Waterproof Walking Toning Shoes WoMens 11NIKE CLASSIC CORTEZ NYLON SNEAKERS WOMEN SHOES BLACK/WHITE 749864-011 SZ 10 NEW , New Womens Ahnu Belgrove Wine Walking Trail Sport Water Resistant Shoes , NEW WOMEN'S SAUCONY GRID CATALYST SIL/FUS/PNK RUNNING SHOES SIZE 6Vans DIGI HULA - AUTHENTIC Shoes NEW ALOHA Hawaii size 5 NEW ,
"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."