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.Aerosoles Lovely Slip-On Low Wedge Loafers, Dark Blue, 6.5 USNine West Black Man Made D'Orsay Low Wedge Ankle Strap Flats 7.5M , andy-05 Slip On Casual Party Ballet Flat Office Oxford Women Shoes Black 8 , AGATHA-01 New Nubuck Fashion Slip On Casual Women Flats Office Shoes White 8.5 , CLARKS INDIGO 9 Black Leather CHARLIE Penny Loafers Flats - 61263 , Cole Haan Womens Peep Toe Heel Rose Pink Metallic Size 8 B Air Soles 3"New Earth Spirit White Sandal Size 6 Leather Beach Casual Open Toe Shoes , Womens 7.5 B M Cole Haan Sabrina Loafer Black Haircalf Shoes Slip-On Ballet Flat , Clarks Slip On Mules Size 11 Adjustable Strap Leather Upper Burgundy Shoes S3Dansko Women's 40 (US 9.5-10) Mahogany Brown Slip-on Loafer ShoeFarylrobin Womens Tina Espadrilles Shoes Yellow Size 7 NewMERRELL MOC MESH SLIP ON MULES SHOES WOMENS SIZE US 6.5 Tan NICE!Spring Step L’ARTISTE Open Back Red Leather Clog Shoes-Vanessa-40(US-9) New * , BORN Pink Bow Leather Ballet Flats Flip On Women's Shoes Size 10Dr Doc Martens Shoes Size US 6 Brown Crazy Horse Leather 5 Eye 8053 90s , Born Womens binga Leather Closed Toe Mules, Black, Size 8.5 F8S6Klogs Harper Womens Clog Shoes Display Model Leather Black Blgr 9MNike Ladies 6/36.5 Zoom Winflo Running Trainers DynamicWeb Athletic SneakersWOMENS NEW BALANCE 980 WALKING SHOES CREAM LEATHER WW980CL SIZE 11 DWomen's Blue, Gray SKECHERS Quick-Fit GoGa Mat Sneakers Size 8.5 M GREAT Con , Adidas Samoa Red White Low Top Sneaker Womens Reto Shoes 7.5Women's Nike Air Max 2012 training running shoes size 8 purpleReebok Royal Tenstall Running Women's ShoesTretorn Tournament Net Sneakers - Women's Size 7 - White , Reebok Ul 6000 Casual Women's ShoesSPERRY WOMENS IVORY OFF WHITE A/O AUTHENTIC ORIGINAL BOAT SHOES SIZE 5Sneakers and Athletic Nine West Obliviator Grey/Silver Synthetic , Clarks Women's Juliet Monte Slip-OnNew Nike Flex Adapt TR Lady Training Shoe 831579 001 Dk Gray/Black/Stealth/White , NEW - Easy Spirit EXPLORER Women's EZStretch Black Suede Slip-on Athletic Shoe 9 ,
"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."