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.Joseph Stewart "NAVY sLIDE MUES LEATHER LINING AND UPPER 8 , Spot On F8826 Ladies Black Studded Flat Shoe (30A) (Kett)Rocket Dog Leopard print loafers 9.5M womens (lightly worn) , Paul Green Munchen Black Soft Leather Square Toe Slip On Shoe US 8 , KS35 Jazmin Loafer Flats 024, Black, 9.5 USAdrienne Vittadini Womens Ganesa Closed Toe Loafers, Black, Size 8.5 YfRPBen Sherman Ladies Blue+Red Fancy Wedge Heel Ankle Strap ShoesThe Fix Women'S Emma Pointed-Toe D'Orsay Ballet Flat, Wine, 9 M Us , SAS Tripad Comfort Silver Leather Loafers Womens Size 8S USA Made Slip On ShoesTorrid black faux suede Classic Heels Women's Shoes size 13 Wide New Without BoxPropet "Opal" W3721 Taupe Suede Mary Jane Comfort Shoes Women's Size 7.5 X(2E) , crocs Duet Max Mesh Print Clog Unisex MuleWomenUS/9 Men US- Choose SZ/Color.Escarpin FUGITIVE talon bride compensé ballerine sandale moc Cuir 40.NEUF. , L.L.Bean Classic Clogs ~ Women's US Sz 10 M ~ Tan Nubuck Leather SC8 , MANAS Leather Wedge Sneakers Size 37 HAND MADE in ItalyVintage PONY Deflector Womens Training Workout Shoes Size 9 Low Sneakers Blue , Merrell Mary Jane Women's Grey Mesh Shoes Sz 9.5Women's Asics GT-1000 Shoes Sneakers Size 8.5 Running Gray Blue White O13Women's SKECHERS 21552 BIKERS SOLE ATTRACTION Beige Slip On Shoes US 9 M , BROOKS RAVENNA RUNNING SHOES - MULTI COLORS ( SIZE 8.5 ) WOMEN`S , New! Womens Skechers 11717EW Synergy Trend Setter Athletic Shoes Black B33Women's Red Christmas Slip-On Exquisite (in) Workmanship FlatsNike Court Lite 845048-400 Womens Shoes Comet Blue & WhiteLast one! Jeffrey Campbell green/yellow plaid low top sneakers sz 7.5 , Women's Nike Air Max Correlate Trainers Sneakers Purple/Silver SizePuma Fenty by Rihanna wmns trainers sneakers eu 39 us 8.5adidas Adilette CF Plus Women's Black/Vapour Grey Met/Trace Maroon B42206 , VANS Style 23 V (Boom Boom) Silver Sage/True White Prison Issue WOMEN'S 8ASICS GEL?Fit Yui Training Shoes, Women's Size 9.5, Black , Merrell Womens - Black Walking Shoes Size 9.5 (414483)
"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."