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.Dear Foams PEACH/LIGHT BROWN Faux Fur Ballerina Flats 9 For Women NewKEEN Women's Coronado Mary Jane 5348 Gray Canvas Slip On Sneaker Flats Size 6Rajasthani Women Blue wedge Sandals Ethnic S Flip Flops Casual Shoe Flat Slipper , NEW Women's Platform Wedge High Heels Booties Ankle Boots Fashion Low Shoes 5-10 , Womens Flat Espadrilles Ladies Ankle Studded Strap Summer Holiday Sandals Shoes , BCBGeneration Womens Nikkola Suede Pointed Toe Loafers, Tan/wheat, Size 6.0Clarks Artisan Dark Purple Suede Daelyn Monarch Slip on Comfort Loafer NEW , Puma Running Shoes Women's Size US 9.5, Free Computer Refresh With PurchaseWomen Flat Summer shoes Pointed toe Ankle Strap Buckle Rivet Leisure pump sandal , BROOKS Adrenaline GTS 15 Womens Running Shoes Size 10.5 Purple Blue , Star Wars Darth Vader Slippers M 9/10 3775 , New Steve Madden Mens Pfire Navy Moccasin Slippers Size 13Asics Gel 1140V Women US 8 Blue + White Athletic Running Shoes J32Vintage 90s Reebok Classic New Womens 6.5 Walker Wide II Casual Walking ShoesRocket Dog Women's Clarita Beach Canvas Cotton Fashion Sneaker Grey 6 M USNEW Reebok Print Athlux Shatr Women's Running Shoes- Black Purple size 9Fila Running Shoes Womens Size 6.5M Blue Teal Black Coolmax -4610 , Women's ARCHE,ballerines laius bleu 37 Carmel, Delicate Flats , Black And White Leather High Top Sneakers Size38ASICS Women's GT-2000 5 Trail Runner, Aluminum/Silver/Orchid, 7 M US , MSRP $190.00 PUMA WOMEN'S THE TRAINER HI BY FENTY WHISPER WHITE SHOES SIZE: 7.5Saucony Men's Kineta Relay Reflex Running Shoe - Choose SZ/Color , Saucony Running Shoes Women's Guide 10 Road , Light Size 9.5 US 41 EUR Wide , New Womens New Balance 5000 WXC5000Y Track Spikes MSRP $125Hoka One One Clifton 2 True Blue/Sunny Lime Road Running Shoes 9M , Converse All Star Velvet Hi Women's Dark Sangria/Black/Turtledove 558992C , ASICS Womens T696n GlacierGray/Bay/White Running Shoes Size 7 (414677) , Womens Mixed Colors Canvas Rhinestones Tassel Sneakers Fashion Casual Shoes D313 , Hard To Find! SUPRA 'VAIDER' Metallic light CHARCOAL PINK WHITE Ladies 9.5 , Women's ADIDAS Cloudfoam QT Racer - Black/ White/Pink Shoes - SIZE 7.5 - NICE!
"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."