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.02-1494 Munro Pisces - Women's SANDALINO KID SUEDE SIZE 8M , ANDANINES VILLENA GIRL'S SHOES SIZE 24 EURO - 8 U.S - MADE IN SPAIN , Sperry Top Sider Boat Loafer Moc Toe Slip on Women US 7 Brown Leather MeshDR. SCHOLL'S BLACK LEATHER MEMORY FOAM BALLET FLATS (sz 9-1/2) , Klogs Abigale Women's Polyurethane Clogs Display Model Shoes White 8 WSole Diva Aliyah Ruffle Pump Wide E Fit In Womens Size US 10 / /Klogs Polina Women's Clogs Display Model Shoes Midnight Apache 10 M , Cole Haan Pink Velvets Ladies Loafers, 9.5Rachel Zoe Damon Cobalt Royal Blue / Red Suede Leather Studded Zip Flats 7.5 8 9 , SPERRY Top-Sider A/O Brown Leather Designer Fashion Studded Flats Boat Shoes 6.5Vionic Women's Snug Eloise Velvet Slide-On Slippers BlackSANUK Pair O Dice Suede SE Women's Animal Print Sidewalk Surfer Shoes Size 6 NEW , TSUBO Womens Size 8 US 38 EUR Beige Leather And Mesh Athletic Shoes , New Balance 1210 Leadville | 6 Women's | New (see details) |Trail Running , Vince Camuto Womens Patty2 White Fashion Sneakers Shoes 6 Medium (B,M) BHFO 6105NORTH FACE MARY JANE SNEAKER WOMENS SHOE SIZE 7.5 7 1/2 BROWN SUEDE FREE SHIP , Propet Women's Travellite Walking Shoe, Silver, Size 6.0 , Women's Born Black Leather Shoes 8 Clients First FlatsSkechers Go Walk Move Arctic Fitness Women's Shoes Size , Skechers Women's BOBS Plush Peace and Love GrayNike Womens Flex Trainer 7 Running Trainers 898479 Sneakers Shoes 002 , 2018 WMNS Suede Platform Core SZ 8 Puma Black Puma White 363559-02Asics Gt 2000 Grey/Pink Running Shoes Women's US 11 (B4,15) , Vans Iso 1.5 Mesh Ultracush Pewter Ballerina Women's Size: 7 , Zoot Solana 2 Running Shoes, Women's 8, NEWSaucony ProGrid Integrity ST 2 Athletic Shoe - Women's Size 6, BlackBrooks Ghost 8 Womens Athletic Running Training Shoes Size 8 Gray Blue PinkPuma Swype Running Shoes - Womens , Adidas Womens Aw4323 White/White/Black Fashion Shoes Size 6 (424272) , TEVA Womens Original Slide Patent Leather White Universal Trail Sandals US 6 NEW
"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."