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.Taos Women's Leather Upper Mary Janes Size 11-11.5 ;Tom's Women's Black Glitter Flat 6MAEROSOLES, WOMEN'S NEW Khaki/Beige Leather Ballet Flat Shoes Size 9.5M , CLARKS BENDABLES WOMENS BROWN BACKLESS LEATHER LOAFERS 3" HEELS SIZE 11 , Womens Print Slides Loafer Slipper Mule Spring Summer Shoes Flower Stylish HotNew Women's Eddie Bauer Delight Pine Leather Mary Jane Shoes Size 9.5 MSRP $70CLARKS Womens Caddell Denali Fabric Closed Toe Loafers , Womens 9.5 40 Keen Golden MJ Potting Soil Brown Leather Mary Jane Shoes ComfortNew! OKA-b Eco-Friendly Jelly Comfort Flat in Blue Size: M-L (8.5-9.5) USJESSICA SIMPSON METALLIC BRONZE FLATS IN GREAT PRE-OWNED CONDITION , Merrell Topo Curve Women’s 10 Brown Air Cushion Suede Slip On Loafer Shoes$69 size 6.5 Alfani Aleaa Pewter Ballet Flats Slip On Bow Womens ShoesNEW***AEROSOLES Sz 6.5M comfort LOAFERS navy blue!! , Calvin Klein Maisha Scalloped Edge Ballet Flats, Deep Navy, 6 US / 36 EUAnne Klein II Black Flats Size 8 , Adam Tucker Womens waves Closed Toe Mules, blknap, Size 10.0 wjXb , POLO-4-17 WOMEN METALLIC SNEAKER CAPE ROBBIN GOLDEasy Street Women's Chella Mule - Choose SZ/Color , NEW Skechers Ladies Slip-On Shoe Memory Foam Black White , New Ugly Me Men's Faux Leather John Moccasin SlipperNike Moto 6 Women Silver, Red & White Walking Sneakers Size 8-MNike Zoom Plus + Running Shoes, Grey/Red/Slvr, Womens US Size 6 , Reebok Running DMX Ride Grey/Purple Womens Size 8 s49Women's ballet flats New Style FlatsWomen's Tahari Foley Women's FLATS Black Year-end Bargain Sale Flats , Women's CHINESE CLOTH LADY'S SLIPPERS/SHOES Clearance Price Flats , Skechers Work Women's Sure Track Trickel Slip Resistant Shoe , Women's Saucony Freedom ISO Running Athletic Shoes S10355-20 Heathered ChromeNEW Superga X Jennifer Meyer Baby Blue Palm Trees Tennis Shoes Sneakers- 40 9 , nike lunarglide 4 Running Shoes Sneakers Women Size 6.5 Green Color ,
"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."