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.KEEN Sterling City Womens Size 9 Brown Nubuck Ballet Flats Slip On Shoes 1007708 , Trotters SHOES WOMENS SIZE 7 1/2 M HOPE , Josef Seibel Women's EU38,US 7.5 Black Leather Block Heel Strap Bicycle ToeGrasshoppers Corin Loafers, Women's Size 9 M, BlackWomens Shoes 9 M JOAN & DAVID Couture Dress Flat Italian Alligator , CLOUD FOOTWEAR Tan SOFT LEATHER sneakers PORTUGAL shoes Womens Size 37 US 6Steve Madden Womens EvanGel Fabric Closed Toe Loafers floral Size 9.0 , Bzees Tempo Jane Shoes Womens Mary Janes Shoes Low Heel Blk Sz 7Womens Havaianas Slim Tropical Beach Summer Rubber Lightweight Flip Flop US 6-11 , Cole Haan Womens Gray Grand.OS Leather Driving Loafers Moccasins Size 8***NEW*** Gola Quota Leather Women`s Sneaker Size 5DollHouse Brand New Red w/ Cheetah spots Size 10 women's , Vintage 70s Euro Granny LEATHER Comfort Oxford Crepe Soles SNEAKERS 10 AA 41SPERRY TOP-SIDER Women's MARINER DOUBLE GORE Slip-On BOAT SHOE Style 9266545 6mASICS Woman's Running Shoe Gel Nimbous 16 T485N Pink SZ 9.5 Purple , Womens Saucony Grid Stratos 5 Silver/Pink Trainers Size 9M (V785) , New Balance 1080 v4 Women's W1080WP4 Athletic Running Shoes White/Pink Size 5.5 , FILA Memory Xridge Womens Size 7 Grey Running Athletic Sneaker Shoes IP-434VIBRAM Fivefingers Treksport 13W4304 Grey/Aqua Barefoot Running Shoes Sz 6/37LADIES SZ 7 M COLUMBIA TECHLITE GREY BLACK GREEN ATHELETIC SHOESBlowfish Malibu Fashion Sneakers Gray Textile Women6.5Medium (B, M)Saucony Triumph ISO 2 Women's Running Shoes Sz US 10 M (B) Blue S10290-2Women's Luxe Feel Slide On Flats Exquisite Flats , Women's Ralph Lauren Womens Size 9.5 Numerous In Variety FlatsConverse Womens 555948C Breakpoint Ox Fashion Sneaker Shoe SIZE 10 NWOB , VANS SK8-HI MOC (PEANUTS) DOG HOUSE BONE SNOOPY JOE COOL SZ 8 WOMENS / 6.5 MENNIKE OVERPLAY VII WOMEN'S WHITE/BLACK CASUAL SNEAKERS sz 7, , Lemare High-top Women's Sneakers with Hidden WedgeVANS Tazie SF Black/White UltraCush Casual Skate Shoes WOMEN'S 10 , Reebok Easy Tone Smooth Fit Shoes Women's Size 10 Black Pink
"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."