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.Aerosoles Womens Fawn Suede Mary Jane Flat Loafer Shoe - Size 9.5MLadies Spot On Formal Loafers F80121Torrid Women’s Size 11W Wide Chambray Stud D'Orsay Light Denim Flats Shoes NWT , CLARKS Gael Angora 26102167 Wo's 10W Crocco Embossed Gray Patent Leather LoaferWomens Llife Stride Burgundy Slip On Shoes Size 9 1/2 , ECCO Biom Women’s Size 7 M (37 EUR) Beige Nubuck Leather Comfort Flat Shoes , TRES RARES CHAUSSURES HAUT DE GAMME DDP T 40 CUIR ROUGE VERNI ETAT NEUF ACHLifeStride Women's Adele Flat, Black,6 W US , vv THE LEATHER COLLECTION BLACK LEATHER LOAFERS 8 M , FRYE Regina Pointed Toe Black Vintage Soft Leather Ballet Flats Women's Size 10US Shoe Size Women Ballet Comfort Light Flat Slip On Stylish Casual Fashion NewDakota Quad Lite Steel Toe Steel Plate Women's Grey Sneakers 8.5MWomens Fashion Girls Mesh Wedge Heel Sneakers High Top Rhinestone Summer Shoes@Merrell Women's Dark Shadow Avian Light Ventilator Blue Gray Hiking Shoes Sz 7.5 , New Call It Spring Womens Ryua Black Synthetic Fashion Sneaker Size 9Vans Women's Solana Sf Desert Floral Ankle-High Canvas Skateboarding ShoeWomen's Salomon XMission 3 Used shoes Hiking/Trail Size us 9.5-B , Women’s Nike Lunarglide 3 Running Tennis Shoes Black Pink Blue Sneakers Size 7.5 , New Skechers USA Gray Metallic Slip On Casual Summer Active Wear Shoes 7 , New Balance Women 990v4 Running Training Shoe W990DM4 MADE IN USA Size 6 B NewLacoste Carnaby EVO 317 & 417 SPW Leather Women Trainers in Navy Blue & WhiteWomen B39027 Adidas Mana bounce ARAMIS Running shoes white silver sneakers , Merrell Siren Sport Gore-Tex Brindle Leather Hike Trail Hiking Shoes Women's 7Womens Nike Air Max Thea sz 11.5 599409 020 95 97 running shoe 90 270 , FILA Memory Sporter Walking Fitness Train Athletic Shoes Sneakers White Womens , SAUCONY Women's Grid Cohesion 3 -Silver/Grey/Plum- Running ShoePuma Women's Future Disc HST Sneakers Running Athletic Shoes White Pink 7.5 M , Skechers Shape Up Women Size 7Adidas Powerblaze W Women's Running Shoes Night Grey/Silver Metallic/Frost MintVANS New Authentic Slim Spring Multi Textile Vault Lady's size 7 ,
"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."