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.Women's Enzo Angiolini Burgundy Suede Flats/Loafers US8.5MSz Xcelent shape cleanEarth Women's Beetlebug Leather Shoes w/ Monk Strap Black Size 6.5BMerrell "Encore Etch" Women's Brown Nubuck Leather/Textile Clogs Mules 7.5 MWomen's Chinese Mary Jane Floral Sequin Cotton Shoes Slippers Red & Black 5-11Ralph Lauren Country Brown Suede Womens Shoes Sz 9B , Sperry Topsiders Gold Leather Preppy Boat Shoe Driving Moccassin Loafers 6.5M 37New Women's Chaps by Ralph Lauren Clarisa Wedge Sandals - Navy/Tan 8 MJack Rogers Black Suede Shoes 10 M Flats Tasseled Loafers Low HeelsEasy Spirit Women's ESMOTION8 Shoe, natural, 9.5 W US , Aerosoles Womens melange Closed Toe Mules, black, Size 6.5NEW Rockport K59759 Kiran Leather Loafers, Women's Dark Brown - Choose Your Size , Nike Zoom Air Women's 8.5 US Light Gray Running Shoes , Skechers Revv Air Running Shoes ,Silver/Purple, Women's US Size 7.5 , Abound Silver Flats Size 6 Patent Metallic Kiltie Flats Slip On NWOTMarc Jacobs Perforated Leather Flat Shoes-White/Black-Made in Italy (Size 36.5)CONVERSE All Star Women Chuck Taylor Black/Gold High Line Leather Sneaker NWOB , Skechers Shape Ups Womens Gray Pink Walking Leather Size 7NEW WOMEN VANS AUTHENTIC LO PRO BLACK TRUE WHITE VN-0GYQ6BT SKATEBOARDING ORGBZ758 HB HELENE shoes blue glitter suede women sneakers , Hoka One One Sz 7 Kailua Tarmac Trail Running Shoes Women Teal Blue & White , VANS SK8 Hi Reissue CA (Glitch Check) Black/Blue/White Skate WOMEN'S SIZE 6.5NIKE WMNS ROSHE ONE LX BLACK LEATHER IVORY Surprise Pack 881202-001 Womens 10 , ASICS Womens - Black Walking Shoes Size 7 (369146) , P-L-D-M Palladium Valmera Cashpyt Leather Sneakers Women's Size 6-10 93430-001 , Reebok Light Gray Running Shoes w/ Pink Accents Women's Size 8.5 M / 39 EuroSkechers SN12371 Shape-Ups SRR Resistance Silver/Black/Aqua Kinetic Women's 8.5B , Asics GT 1000 Womens sz 7 T5A8N WIDE Silver/Pink/Green Running Training ShoesNike Women's Lunarglide 8 Running Shoes AA8677 500 Violet/Green/Black, Pre-OwnedBlue Butterfly Woman Girls High Top Sneakers Casual Comfy Skate Vulcanized Shoesadidas NEO Women Cloudfoam Super Flex w Running Shoe Pink/Black/White, 10 M US ,
"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."