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.Waldläufers Gigi Gitta slip on loafer flats black reptile patent leather comfortSANDALES SOIR DE LUNE MOD.LOVE NEUVES !!!!Ladies Womens Flat Low Wedge Platform Heel Diamante Holiday Summer Sandals Shoes , Rieker Antistress Hillary Womens 8.5M Euro 39 Brown Leather Loafers VGC!!! , BANDOLINO, LIKE THIS, FLATS, WOMENS, PEWTER, US 8M, PRE/OWNED , ECCO Womens Black Leather Square Toe Casual Oxford Shoes Size 6 #C96 , Vintage STEVE MADDEN Brown Leather Platfrom Wooden Wedge Clogs Mules 8m suede , Dansko Brown Leather Slip On Clog Mules Comfort Shoes Size US 10.5-11 /Nanette Lepore Black Cool Design Sneaker Size 7.5EUC BORN Women's Shoe Clog Mule Slip On Buckle Accent Brown 8 M 39 #W965514 , New $100 VADO Ballerina Women"s Shoes LEATHER Narrow Pink Size 7 USA/38 EURO. , Aldo Womens Sz 7.5 Flats Loafers Asian Print Metallic Point Toe Black Multicolor , Brand New Red Plaid Canvas Slip on Loafers Moccasin Comfy Flat Women ShoesZara Women Suede Sneakers With Feather Detail Size 6.5 NWT , JBU Womens Navy Misty Encore Flats Shoe Size 7 M , Women's Cole Haan Black & White Leather w/ Patent Leather Ballet Flats Size 7 B , New Jambu Blush - Barefoot red women's shoes size 6.5PIN UP COUTURE Russell-34 Series2" Block Heel Retro Rockabilly Vintage FlatsClarks Everlay Dairyn Slip-On Wedge Loafers 290, Dark Tan, 7.5 US / 38 EUGrasshoppers Women's Cleo Wedge Sneaker Black Size 10.0 APmT , Cole Haan D15552 Red Stitched Water Proof Walking Mules Women's US 8.5 BNIKE TRAINING WOMENS FREE XT QUICK FIT + SHOES WHITE BLACK VOLT 415257-100 SZ 9 , Asics Gel-Trabuco 11 WR Trail Runner Red Gray Athletic Shoes Women's 6 US EUC , Reebok Women's Classic Leather Golden Neutrals Fashion Sneakers 8.5 BM USReebok CN1799 Women Triple Hole 7.0 Running shoes grey Sneakers , Superga Women's 2790 Black Leather Platform Fashion Sneaker Size US 9.5VANS Authentic (Neon Lights) Western Black Skate Shoes WOMEN'S 7Nike Reax Run 5 Women’s Running Shoe Size 9.5 White/Silver/Blue EUC!Propet TravelActiv - Women's Flexible Travel Comfort Shoe - All Colors - All Siz , ASICS Women's GT-1000 6 Running Shoe Sz 10 US ,
"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."