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.PRIVO by CLARK'S Women's Brown Suede Perforated Brown Leather Shoes Size 9.5 MSkechers BOBS Womens 2nd Take-Plush Animal Slide Sandal- Select SZ/Color. , Rockport adiprene by adidas black women's 6M leather/suede ballet slip onsTommy Hilfiger brand women athletic casual shoes size 7.5 canvas upper grey YN7 , Clarks 9.5 M White Leather Driving Mocs Dunbar Racer Boat Shoes Flats Loafers**Havaianas Origine Li Espadrille Flat - Women's Size 10W - Natural , *SHAPE BY ECCO LADIES BLACK LEATHER VELCRO SHOES SIZE US 8 M /UK SIZE 5.5 , Lauren Ralph Lauren Danita Espadrilles 994, Chiffon Pink, 9.5 US / 40.5 EUIsaac Mizrahi Loyal Denim Blue Pleated Bow Ballet Flat 9.5 NEWMe Too Women’s Legend MAGENTA Patent Leather Ballet Flats-Size 6.5-NIB , Shoes Of Prey Women's Black Leather Ballet Flat Size 5 W Buckle $139 , A2 by Aerosoles Time Limit Round Toe Flat Slip On Loafers Choose Sz/ColorWomens Canvas Embroidery Floral Hidden High Wedge Platform Creeper Sneakers X774Adidas Cloudfoam Advantage Clean Sneaker - Women's Size 7.5 White , Ryka Moxie women's Athletic Running Sneaker Shoes Size/8.5Adidas TR 9 Women Running/Walking/Tennis Shoes Size 5.5VANS Off The Wall HELLO KiTTY pink print skateboard sneakers shoes Men 5 Wmn 6.5 , Merrell Siren Sport Hiking Shoe Womens 6.5 Brown Tan performance outdoor , Skechers 12807 Encore Womens Size 8.5 , CONVERSE 6.5 Womens Gray Silver Metallic Thread Hi Top CT Chuck Taylor All Stars , WOMEN;S ADIDAS ORIGINALS VESPA SHOES SIZE US 5 G15782Women's J.Crew Textile Loafers Size 9 To Adopt FlatsPropet W3851 Womens Slip Resistant Wash N Wear Slip On II Walking ShoesFrench Bulldog On Black-Women's Running Shoes-Free ShippingVans Crystal Blue / True white Sk8 Hi Slim Shoes Sneakers TrainersWomens Skechers Shape-ups Shoes Size 9.5 White Walking Toning Sneakers 11800Skechers Studio Comfort - White - WomensKangaroos Womens Zipper Pocket Tennis Shoes Sneakers Blue Pink Size 10 , Propét Womens Stability X Strap Low Top Fashion, Black, Size 10.5 , DIMMI WALK SHOES SNEAKERS 6 TAN BROWN ATHLETIC GLADIATOR STRAP COMFORT STYLE NIB
"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."