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.Mojari Indian Women Shoes Leather Flip-Flops Ballet Flats Jutti Flat US 7 , � Isaac Mizrahi Ballet Flat Loafer size 9 M Tan Brown Leopard Leather; StrapsWomen's Chinese Mary Jane Floral Print Cotton Shoes Slippers - Sizes 6-10 NewFranco Sarto Womens scranton Leather Pointed Toe Mules, Black su, Size 11.0 aiDh , Etienne Aigner Emory Loafers Cognac Brown Women’s Size 6 M Gold Metal Accent EUCWOMENS LUCKY BRAND BROWN CLOG CLOGS BIRKINSTOCK SHOES SIZE 9 *EUC , ** Easy Spirit Barton Loafers-Women's size 6.5 BlackStegmann Wool Felt Clogs Shoes Womens 9.5 Green Holly Holiday Slip On , Rockport Lizzie Stone LTHR Slip On Size 9.5N D605/Merrell Encore Moc Q-Form Ortholite Brown Suede Comfort Women's US 10 / , MEPHISTO womens us 10 leather slides shoes cool air cordovan excellent , Splendid Jaime Brown Womens Shoes Size 7.5 M Flats MSRP $98 , PUMA IOCELL 1.0 Gray Pink Women's Shoes Sneakers Size 9.5 FREE Shipping!Womens Black FILA Radiant Casual Shoes Size 8 SC10131-010Vans Casual Sneakers, #TB6Q, Black/Multi, Womens US Size 7.5Dr. Scholl's Giorgie Flats - Women's Size 8.5 M, NavyNew Vans Womens Leah Canvas Casual Athletic Shoes US 7 , Men Rainbow Sandals Single Layer Hemp Top & Strap with Arch 301AHTS Color Brown , New Balance 425 Running Shoes, #WR425TBN, Grey/Teal, Women's US Size 10Skechers Performance Womens Go 4-Airy Walking Shoe- Select SZ/Color.90s Converse High Top Floral Yellow Flower Daisy Canvas Platform Sneakers , W0MEN'S SZ 7.5 SKECHERS "GO WALK 4" WITH MEMORY FOAM ATHLETIC SHOES BLACKIMAN Womens Runway Chic Luxurious Slip-On Sneaker - Black Size US 11Danskin Now - Women's Shape-Up Sneakers White BRAND NEW IN ORIGINAL BOX , SAS Sporty Athletic Sneakers - Women's Size 8W, Sporty Silver/Blue , NIKE WOMENS METCON REPPER DSX TRAINING SHOESVANS ERA HIKER MTE CA PIG SUEDE FLEECE BLACK VN000310HVZ WOMENS 7 MENS 5.5 SHOESNike Flyknit One Shoes Women's Size 9vintage 1990's White KEDS women's SZ 8 platform slip on backless canvas sneakers , WOMEN'S SKECHERS GO WALK 4 EUPHORIC 14920 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."