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.143 GIRL PANNA CROCHET FASHION FLATS NUDE SYNTHETIC IMPORTED US SIZE 8.5 MEDIUM , Soludos orange melon Espadrille Flats Size 9/40Womens Sz7 Pointed Toe Ballet Flats Black Work Casual Footwear $29.99LADIES WOMENS SPOT ON BLACK BURGUNDY SLIP ON LOAFER STYLE FLATS SHOES F80186SALE EAZE F3091 LADIES BLACK CASUAL SHOE , Banana republic Beige W/ Silver chain front women flats size 10Women's Sperry A/O Ivory Shoes White Leather Boat Shoes Size 10 M , Woman's Franco Sarto Slip on Penny Loafer Shoes Size 7 1/2 M Pre-OwnedAEROSOLES Loafers 11 Black Buckle genuine LEATHER COMFORT FLATS SHOES , Enzo Angiolini Riberao Red Leather Flats sz 11 MARA Croc Embossed Light Brown Oxford Nubuck Rachel Loafers Size US 7Tamaris Women 22134 Ballet Flats sz 37 Brown Ballerinas Leather Shoes touch itClarks Unstructured Un Reisel Myra Sandal- Women's Size 8 W, Black , MERRELL Mimosa Emme Women's Black Leather Mary Jane Slip On Casual Shoes 8M 38.5Zee Alexis Women's Sammi Woven Mary Jane Shoe Black Metallic 6.5 MNew Womens BOBS Flexy Slip On Shoes Size 6 33789 (B3) , Women Casual Athletic Sneakers Breathable Air Cushion Sports Running Shoes , Prada Driving Shoes Moccasins Flats Loafers Tobacco Suede Brown 36 1/2 Cognac , Skechers Womens Bobs B-Loved Round Toe Loafers Black Size 6.5 l6qSPre-owned Nike Air max 360 Running Sneakers Women's Size us 9-BPropet M0095 Mens Cronus Stretch Slip On Shoes Slippers Brown Diabetic Size 8.5Volatile Womens Elevation White Fashion Sneakers Shoes 11 Medium (B,M) BHFO 8452 , Nike womens athletic shoes size 9 5 lot of 2 pair3D Mix Color Fashion Women Running Trainers Mesh Sports Shoes Athletic SneakersWomens Shoes Under Armour CHARGED STUNNER Trainer Sneaker Black Aluminium PewterUSED - Geox Womens D Avery B Trainers SIZE US 8 , ASICS Womens Gel-Craze TR 4 Cross-Trainer Shoe- Pick SZ/Color.Nike Cortez RARE Ultra Breathe in Electric Green! Women's Size 8 New! 833801 300Unicorn Canvas Low Top Shoes Sneakers Style 8 sizes 5-12 womensMBT Womens Trainers Fitness Toning SHOES White w/ Blue Sz. 8 US /3 5 UK ,
"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."