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.Reef Women's Ocean Mist 2 Shoes - Multi , Ladies Anne Michelle Slip On Dolly Shoe 'L4946' Available in 2 ColoursWHITE MOUNTAIN Black Suede LOAFER SHOES with Leather Backs; Slip-On; Bows 7MMERRELL Encore Groove Pro Slide Sz 6 Women Slip-On Mules , New Zara High Heel Velvet Platform Sandals size 6.5 US Second item ships freeSperry Top-Sider Marion Black Crinkle Pate Women’s Shoes Sz 6 NWBNAOT Kirei Black Suede Patent Leather Trim Mary Jane Comfort Shoes Sz 41/ 9.5 , Geox Respira Womens Loafers Size 37.5 Black Leather Slip On Comfort ShoesKlogs Womens Navy Blue Non-Marking Slip Resistant Clogs Size 9 , Nine West Womens Norella Leather Almond Toe Loafers, Cognac, Size 8.0 yFh3SAS Tripad Black Leather Loafers Shoes Mary Janes Womens 10 N , Salomon Road Trip Beige Mesh Sneakers US Women's 9 /3 Fast ShippingDenver Hayes Wedge Casual Women's Black Shoes 11MBandolino NEW 6 M "Emalita" Metallic D. Silver Leather Flats Studs detail 1" , Anne Klein Womens Buttons Cap Toe Ballet Flats Brown Size 5.0K-Swiss Women's Pink Suede Blue Denim Sample Sneakers Size 7 - RARE , **Steve Madden Ecntrcqt Slip On Sneaker - Women's Size 9.5B, Olive , Nike Air Vapor Advantage Blue Tennis Shoes Womens Sz 7.5Vans Authentic Hamburger Shoes Food Late Skate Shoes Women's 7 Kids 5.5 New NIBWomen's Ellie Women's Lolly-609 Promotions Athletic ShoesWomen's Ladies Spot On Brogue Shoes The Cheapest Flats , Nike Free Run+ 3 Womens Running Shoes Laser Purple/PR Volt-Black-VLT Size 5.5 , Converse CT Rubber Hi Tops, Cyan Space Blue/ Black Sole- Women's 9.5 NWOB , Ahnu Sugar Venture Sneaker, Women's Size 7.5, Light Brown , New women's Sneakers Chic Shoes Sequins Hidden Heel Wedge Sports High Top Size , Women's Puma Ignite v2 18861207 Black-White-Pink Glow Brand New in Box , New Balance 574 Classic Running Sneakers Encap Blue Womens Sz US 9.5BBrooks Addiction 10th edition Size 6 Running Gray Maroon Silver Good Condition , Sperry Top Sider Womens Shoes Size 8.5 Ivory Textured Flat Slip On Sneakers , Women's Asics Kayano 20 Black Running Shoes Size 8.5 ,
"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."