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.Keds Womens Tournament White Casual Shoes Sneakers 8 Medium (B,M) BHFO 0033 , Nine West Noinstride Slip Ons Women’s Size 6 MediumClarks 7 Womens Red Leather Slip-on Open-back Comfort ClogsBandolino flats shoes 6.5 M calf hair leather leopard print , Born Concept Womens Brown Leather Slip on Loafers Size 8.5 M , Privo by Clarks Loafers Flats Ballet Black Leather Women Shoes Size 9 , New Womens Low Block Heel Studded Spike Chelsea Pull On Ankle Boots Faux Leather , MERRELL Mary Janes Shoes size 8.5 Womens Circuit MJ Chocolate Cordova , Cynthia Vincent Women’s Shoes Flats Ballet Black Embroidered Toe Size 7.5 E85ECCO Light Shade Black Leather Three Strap Walking Shoe Womens US 8 8.5 , Vince Camuto Womens Lemel Leather Almond Toe Ballet Flats, Grey, Size 8.0 qZNS , Nine West Sholette Flats - Women's Size 8 M, Black** Dr. Scholl's Giorgie Flats - Women's Size 7.5M BrownDolce Vita Camden White Womens Shoes Size 6 M Flats MSRP $100DC Skateboard Shoes Womens Rebound High Top Size 9 Neon Orange Blue Green PinkG by Guess Black & White Tiger Stripe Sneakers Size 8MDANSKO BLACK LOAFERS SHOES WOMENS 40 9.5-10 LEATHER MARY JANES FREE SHIPUsed Nike Free 4.0 V4 Women's Running/Training Shoes Size sz 8.5 Pink Blue White** New Balance 1065 Lightweight Walking Shoes, Women's Size 6 D, Grey/Pink , Ted Baker Youngi 2 Mens Green Navy Textile SlippersPuma G. Villas Pink/white Casual Atheltic Shoe Womens Size 9.5 , BEBE SPORT DANE WOMEN Sneakers (6M, Grey) , KEEN Arcata Blue Nubuck Leather Casual Skate Sneaker Shoes Women's 8 SHIPS FREESaucony Original DXN Trainer Women's Running Shoes Size 9.5 S60124-40 GRN , Nike Structure 13 Trail Running Shoes Athletic Sneakers 386408- 061 Gray Size 7 , Vans Authentic White Canvas Unisex Skate Trainers Shoes , Nike womens Free 5.0 TR FIT 4 size 9.5 Used 629496 005 sneakers , Vans Sk8 hi Slim White Leather Plaid Women's 9.5 Men's 8 Skate Shoes NewNew Balance WRUSHSL2 Running Shoes - Women's Size 6 B, GreyLori Goldstein Collection Slip-On Faux Fur Moccasin Black Women's Size 6.5
"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."