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.BEVERLY FELDMAN Ladies Black Suede Drving Loafers Size 7M02-2275 Black Born Motola WOMEN'S SIZE 8M , Clarks Women's Gael Beam Loafer Black Size: 6.5W , OLD NAVY SLIP ON STRAW ESPADRILLES FOR WOMEN BLACK AND BROWN SIZES 6, 8,9 AND 10Jutti Indian Banjara Women Shoes Leather Mojari Pointy Flats Flip-Flops US 6-9Earth Shoes Women’s Size 6 Slip-On Brown Leather Hemet Loafers Shoes JC , TERRIFIC 10 N SAS JEWEL BLACK SHOE WOMENS NARROW LOAFERWOMEN'S NUTURE BLACK LEATHER MULES - SIZE 6.5 MEtienne Aigner Women's Leather Brown Shoe Loafers Logo Tassels 8.5 M Slip On EUC , Zee Alexis Womens Melissa Clog Shoes Warm Grey 6.5 MCabello Comfort 5734-11 Womens Leather Flat Shoes Made In Turkey , Eastland Women's Skip Boat Shoe Navy 8 M US , NWOB Tommy Bahama Women's Vista Brown Suede/Leather Slip-On Espadrille size 6.5 , Alice + Olivia Pink Zebra Calf Hair Ballet Flats Shoes, Size 7 , S Sport Women's Gray Textile Slip On Platform Athletic Running Shoes US Size 6 , Chic Womens Breathable Sneakers Hidden Heel Slip On Platform Athletic Shoes S932NWOB Nike Zoom Rival S8 Track Spikes 806554-011 Blk/Wht Womens Racing Shoes Sz 8 , PUMA ArchTec IOCELL 1.0 ~ Pink/Turquoise Athletic Shoes 8.5 * GOOD - VERY GOOD , Nike Free Run 2+ Women Gray/White running athletic Shoes Sz: 9V31 New Balance WL574FAA Tech Raffia Black Suede/Textile Sneakers Women Sz 7.5 BAdidas New w/box Womens XCS 2 Spike Running Track and Field Shoe Sneakers Tennis , Puma Suede Bow Uprising Womens Orchid Suede Trainers , adidas TUBULAR VIRAL2 - Black - Womens , Vans Sneakers Sk8-Hi Nightshade / White, Men 5, Women 7.5. NEW Purple-ish , NEW CLARKS WOMENS TRI FORM - WOMENS SHOES - ICE BLUE LEATHER , NIB Women's New Balance WSTROLP RUNNING Shoes Wide(D)&Medium Width Alpha PinkReebok Triplehall 5.0 Ld Women's Shoes , Women' White Adidas Neo Cloudfoam Sz 8 , Women's Asics Amplica - White/Silver/Porcelain Blue - Width: med - Running , MBT Chapa Stone Leather Physiological Active Women's Toning Walking Shoes 7.5 N ,
"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."