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.A New Day Women's Black Wide Width Velma Slip On Pointy Toe Mules Size 8W NEW , PRE BOBS from Skechers Women's Highlights Flexpadrille Wedge Taupe PK A Size , Steve Madden Womens Jackpot Embroidered Flats Espadrilles Shoes BHFO 5599UNIONBAY Women's Demi-u Ballet Flat, Black, 8 M US , Clarks Slip On 9 M Soft Cushion Collection Shoes Comfort walking Elastic BlueNew Womens BOBS World Cartwheel Slip On Shoes Size 8 34268 (B3) , Women's Born Walking Slip Ons Size 6 (B,M) Casual Solid Brown LeatherMojari US 9.5-12 Indian Handmade Leather Women Shoes Maroon Flip-Flop Oxfords , Jambu Women's Bar Harbor Women's Shoes Sz 11M/Eu 42 Black Loafers Suede Slip-OnKangaroos Shoes Mary Jane Brown Blue Floral Leather Comfort Casual Flats Sz 10M , RIEKER Antistress Doris A6 PAZIFIX NAVY Women's 37 US SZ 6.0 M NEW DISPLAY D7157Nine West Womens Antonecia Leather Closed Toe Loafers, Green Suede, Size 9 , New Quiksilver Womens Aqys700027-Xswg Shoes Athletic Shoes Size 6 , Asics Women's Gel-Surveyor 2 Titanium/White/Sharp Green Running Shoe 11MNWoT Nike Zoom Celor Women 12.5 Pink Silver Reflective Track & Field Cleat ShoesCloud Caliber Gold Leather Elastic Slingback Peep Toe Flats Women's 37/ 6.5-7 US , Maiden Lane Wingtip Leather Low Top Sneaker , Women's Nike Free 5.0 TR Fit 4 PRT Size 7 629832 402 Purple Pink , Black Men's Sandals Sport Slides Beach Slippers House Shoes Slip On Footwear NewASICS GEL KAYANO 21 T4H7N BLUE PINK WHITE RUNNING SHOES US WOMENS SIZE 10.5Skechers Womens Relaxed Fit Memory Foam Black Fashion Sneakers - Size , Women's Sanuk NEW Vee K Shawn High Top Size 10 Olive Green color 1039Womens Flatform Platform Hidden Wedge Leather Trainers Creepers Sports ShoesPuma Carson Running Shoe - Women's Size 6.5, BlackWomens Nike Flex Experience Running Athletic Sneakers Shoes 599548 Size 7 , Women's Bandolino Women's Edition Ballet Flat High Safety Flats , MNX15 Women's Elevator Shoes HUNTERORANGE Height Increase 7cm by FedEx Fast ShipPleaser Women's Classique 01 High Heel Slide Red Kid PU Sandals , Nike Women's Roshe Run LD-1000 Size 7 Steel Racer Blue White Enamel Green Fly , Vans Classic Slip-On VN000EYEBLK Black Size 7.5 Men / 9 Women *NEW NO BOX*
"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."