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.Bare Traps Womens black strappy flats size 12 med buckle strap HAMELA , Fashion Bug Women Brown Flat Shoes Sz: 8 , Pleaser Ballet Flat Adult Women Flats Red Satin ShoesBetsey Johnson Boom White Womens Shoes Size 9 M Fashion Sneakers MSRP $69Naturalizer Saban Loafers, Women's Size 8 M, BlackCLASSIQUES PALLADIUM COULEUR SABLE T40 TBE COLLECTOR VINTAGE A ACH IMM FP RE , SAS 10 Brown Loafers Women's - Missing Insoles , Rialto Comfort Mystical Womens Size 7.5 M Shoes Leather Suede Mary Jane Mules**Delman (08603095) Ballet Flats - Women's Size 6 M, Copper , Brinley Co Womens Comfort Sole Faux Leather Round Toe Flats , J.Jill D'orsay Leather Flats 9.5M Suede , VINCE Kia FLATS Loafers ORANGE Sz. 9 Slip On Shoes LEATHER Retails $198 CHIC! " , Hush Puppies Leather Walking Shoes - Women's Size 8.5, Black , LADIES SHOES/FOOTWEAR -Cherry Kerrie black multi sandal , 8.5 M EMME SPIRE DARK BROWN MJAY MERRELL WOMENS SHOE LOAFER , LifeStride Women's Sevyn 2 Pump, Red, Size 5.0Womens Breathable Sneakers Casual Athletic Running Walking Sports Shoes TrainersFergie Womens Nickel Leather Closed Toe Slide Flats Firefly Leather Size 7.0 , COLE HAAN womens brown leather woven loafers shoes size 6.5 BCircus by Sam Edelman Women's Vanellope-1 Sneaker Gold/Golden Caramel Size 6.5 , Sporto Heidi Purple Suede Sporty Mule 7.5 Mismatched widths Sale , Skechers Go Walk 3-Integral Walking Shoes - Women's Size 8.5 W - GrayNew FREE PEOPLE Purple/Black Velour/Leather Varsity Slip-On Sneaker Size 39/8.5 , 15650 BBK Black Skechers shoes Go Walk Cool Women's breathe Mesh Slip On Comfort , NIKE Women's Flex 2017 RN Running 9.5 Violet Dust/White/Plum Fog/Iced LilacSkechers Performance Women's Go Walk Impress Memory Foam Slip-On Walking ShoeNEW adidas Lite Racer F99661 Womens Shoes Trainers Sneakers SALE , Nike Women's JUVENATE TXT SQUADRON BLUE Running Training Shoes 807423 400 SZ 6.5Womens Merrell Smoke Leather Hiking Trail Shoes Brown Grey Size 7 / 37.5 , Reebok Crossfit Shoes Nano 4.0 Women's Black Shoes Size US 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."