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 New Casual Flat Comfy Ballet Shoes-Black OR White dl89 , ABEO Womens Bio System Taryn Dotted Print Leather Ballet Flats Size 11 *VGUC*Stuart Weitzman 11M Black Ballet FlatSoftspots Women's Black Shoes Size 7 1/2 Medium Clogs Mules Slip Ons Pre-Owned , Rieker Women's Size 9 Brown Leather Mary Janes Shoes , SPERRY TOP SIDER Deck Boat Loafers Flats Mary Janes LEATHER Womens SHOES Sz 7 , ECCO Nubuck Brown Leather Mary Jane Clog Shoes,worn 1x, sz. 40 (9-9.5 U.S.)Womerns Size 8 Keds Blue Polka Dot Canvas Fashion SneakersSteve Madden Women's Hugh Flat Blue Velvet Size 6.5 tFHyAerosoles Women's Rite on Ballet Flat, Red Fabric, 7 M US , Chinese Laundry Women's Gracias Ballet Flat, Hot Pink/Metallic, Size 6.5 , Skechers? ~ GO FIT 3 Shoes ~ Everyday 14085 ~ Women Sz 7.5 ~ VERY GOODEasy Spirt e360 Womens Running Sneakers Athletic Shoes Purple Teal Size 6.5 , New Balance Women's Wx623 Cross Training Shoe,Black,8.5 B US , New Balance 577 Women's Size 8.5 Gray Yellow Reflective Athletic Running ShoesPearl Izumi Running Peak II Womens Orange Gray Shoes Size 7 Colorado Hiking , Women's womens vans sneakers New Varieties Are Introduced One After Another Athletic Shoes , Vans Classic Slip On Suede Sepia Rose Women Sneakers New Authentic Limited VN0A3Women's Nike Air Max Fury Running Shoes Size 7 Grey AA5740 003Kenneth Cole New York Womens Kam Ballet Leather Closed Toe, Storm, Size 6.0 , Vasque Women's Constant Velocity II Size 8 US Ebony/Baltic (VS18W-1) , Nike Air Presto WMNS White Pure Platinum 846290-105 US6 , Adidas Originals Superstar BW35 Slip On Ice Pink BY9138 Size 9.5 , Soludos Platform Tennis Sneaker - Women's Size 8 WhiteNIKE WOMENS FREE TR 6 RUNNING SHOES , ASICS JOLT CARBON MARUSAKI WOMEN SHOES SIZE 6.5 TO 10NIKE WOMENS ZOOM STRIKE RUNNING SHOES #AJ0188-001 , Reebok Women's ZPump Fusion 2.0 NEW AUTHENTIC Grey/Pink /White V72140Nine West Women's Orlov Pony Fashion Sneaker, Taupe Multi, 9 M USPUMA Roma White Pink Sneakers Womens Size 11 Leather Upper Athletic Tennis Shoes
"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."