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.Dr Scholl's Woven Leather Monk Strap Loafers Comfort Shoes Women's Size 6.5 , Studio Works Comfort Delilah Womens Brown Leather Slip On Slim Ballet Flat US 8MNWT Sam & Libby GUNMETAL Gray Silver Metallic BOW Flats Shoes Womens 6.5 M , Trotters Heather Woven Brown Mules Slides Leather Brazil Women's Size 9 M Shoes , Cobbie Cuddlers Womens Shoes Zip Front Brown Leather Low , Doc Marten WomenFlats Loafer Comfort Comfy Round Toe Leather US SZ 5BOC Born Concept Brown Distressed Leather Clogs Women Shoe Size 6 Slip On Wedge , Sperry Top-Sider Women's Bahama 2-Eye Sequin Boat Shoe Size 7.5 MLucky Brand Women’s 6.5 Emmie Ballet Flats Beige LeatherGH Bass Clogs Malinda II Size 8 M Brown Garden Clogs Slip OnWomens Lands End Black Mesh Sport Slip on Mary Jane style 416706 Sz 7.5 D Wide , Rieker Slipper Shoes Leather with Soft Leather Insole, Beige Pepper NEW , Womens Dr. Martens 12163 Sz 8 Brown Leather 2 Strap Mary Jane Shoes , REED EVINS suede multi colored geometric applique ballet flats shoes 9.5 M *** , women's Fashion Casual Sports Sneakers Youths Walking Travel Athletic SneakersBrookhaven navy sneaker size US 9.5/ Eur 41 red christmas collar women high-top , NEW FRANCO SARTO WOMENS DALTON 2 MULE , Womens Faux Fur Casual Block Low Heels Balck Casual Shoes Slip On Lofers Fashion , Calvin Klein Sally White Womens Shoes Size 8 M Fashion Sneakers MSRP $98 , MERRELL SIREN SPORT OLIVE WOMENS SIZE 8.5 HIKING TRAIL SHOES Sneakers , Women's New Balance 940v2 Shoes Sneakers Size 8B Running Training Blue Gray AB7 , Propét Women's TravelActiv Woven Walking ShoeSkechers Women's Bikers - Hyphen Slip-On Shoe , Nike Air Zoom Condition Nike Women's Shoes 852472-005 Wolf Grey/Fresh size 11Steve Madden Womens Bryanne Low Top Slip On Fashion, Black/Multi, Size 6.0 , Asics Patriot 9 Glacier Grey/White/Porcelain Blue Basic Running Shoes T873N-9601 , 12757 Black BBK Skechers Shoes Women Memory Foam Train Comfort Sneaker Flat Mesh , Paperplanes Women Sport Mesh Skin Shoes Athletic Running Shoes 1404 , Ryka Indigo Blue/Silver Womens Running Shoes , New Womens Shoes Fashion Casual Sneakers 10 White Black Skechers Street Zebra
"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."