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.6 1/2 WORTHINGTON FLATS Croc LINDA Womens Sz 6.5M BLUE BELL Escada Loafers shoes , Marc by Marc Jacobs Plaque Patent Ballet Woman's Flats Size 37 , COLE HAAN Womens Manhattan Ballet Flats Shoe Sandstone Leather D39570 Size 6B , LifeStride 7 M golden bronze synthetic cut-out sandal flats braid detail ArielWomen Slip on Round Toe Shallow Mouth Embroidered Casual Ethnic style Shoes R736 , LADIES BRONZE RHINESTONE SLIDES. SIZE 5.5,6,6.5,7,7.5,8,8.5,9Fergalicious Alana Dark Navy Corduroy Plaid Ruffle Bows Ballet Flats Size 8.5 MCLARKS COLLECTIONS Gold Glitter Flats Espadrille modern design worn once size 10 , EARTH Journey Women's Blue Suede/Leather Slip On Loafers Shoes Size 7 BVaneli Fayette Nappa Leather Loafers, Women's Size 10.5M, BlackSkechers Performance Women's Go Walk 4 Interact Walking Shoe, BlackAravon Women's Barbara-AR Fisherman Sandal Blue size 8.5 , LAUREN by Ralph Lauren Womens Berdine Leather Closed Toe Art Creme Size 9.0 LA , Propet W3902 Womens 9.5 M Sneaker Shock Absorber Walking Shoes White (Inv P) , Women New Light Blade Running Shoes Breathable Mesh Soft Sports Casual ShoesSkechers Womens 11936 Grey/White Walking Shoes Size 8 (361116) , Converse Chuck Taylor All Star High Top Rhinestone size 7 , NEW Beloved WOMENS HIGH TOPS SHOES ICE CREAM DRIP US 6-12 CUSTOM MADE TO ORDER , PUMA Women's Pulse XT PWR Cool Cross-Training ShoeALDO Women's Lansdale Fashion Sneaker, Navy, Size 7.0 , NEW WOMEN SKECHERS YOU TALK MOVEMENT BLACK WHITE MESH FABRIC UPPER 14951 ORIGINANike Dart 10 X Running Cross Training Workout Blue Mesh Sneakers Shoes Womens 6 , Womens Sequins Paillette Leather Buckle Fashion Athletics Sneakers Hidden Wedge , New Balance Fresh Foam Arishi Shoes Gray warislo1 Womens Size 9.5BWomen's Nike In Season 5 Running Shoes Size 6 Gray 819033-013 Training TR MemorySaucony Women's Xodus Iso Ankle-High Running Shoe , Asics Gel-Frequency 3 Athletic Shoes - Women's Size 8.5 D, Navy/Silver/BermudaNew Women Wild Diva Cala-23 Faux Fur Patch Fuzzy Slip On SneakerASICS Women’s Gel Unifire TL Running Shoes 12 D16 , Taupe Skechers shoes GO walk 3 Women Fashion Comfort Casual Slip On 14610
"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."