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.SLIP ON LOAFER BY NATURALIZER "NATURAL SOUL" US SIZE 6 BLACK LEATHER UPPER , Women's Clarks Black Slip on Pebbled Leather Loafers Clogs Size 6 MDr Comfort Women Paradise Light Green Leather Mary Jane Therapeutic 7.5 M #K12 , Isaac Mizrahi Loop Tassel Nut Brown Suede Moccasin Flats New , Women's Sperry Top-Sider French Blue Snuff Suede Boat Shoe/Loafer Sz 6M MINTY!Sam Edelman Women's Shoes Size 10M Slip On Thong Wedge Brown , Keen Cusho Casual Burgundy & Gold Driving Flats 9 , The Sak Womens Echo Fabric Closed Toe Slide Flats Grey Felt Size 6.0Clark’s Women Artisan Ruthie Twist Clog Burgandy Red US Size 8M 85123 , Dolce Vita New Taya Black Womens Shoes Size 8.5 M Flats MSRP $120 , ZARA SHINY HEELED LEOPARD PRINT COURT SHOES MEDIUM HEEL SIZE US 9 , GUESS Jeans Shoes Flat Flats Heel Flip Flops Sandals Flop shoe Ballet NIB 6.5 , New Women's White with Silver Studs Flat Fashion Sneaker Sz. 6 1/2" , 2018 Autumn New Rabbit Fur Shoes Womens Fashion Genuine Leather Loaders ShoesSTEVE MADDEN Womens 'Rhode' Nude Suede Platform Slip On Sneakers Sz 9.5 - 231947Asics GLS Womens Size 6.5 RN A640312CS Black & Pink , Nike Women's Flats Ballet Dance Training Athletic Pink Size 8.5Grasshoppers Women's Cleo Wedge Sneaker Black Size 10.0 APmTChuck Taylor Pink Converse All Star Size 6Skechers gostep black slip on womens flat athletic performance comfort 8 medium , Adidas Performance BY8890 Womens Powerlift.3.1W Cross-Trainer-Shoes 8 , New Skechers Womens Relaxed Fit Bikers Orchard Clog Slip On Shoe Black/WhiteNike WMNS Juvenate Flo Print Flowers women lifestyle casual sneakers aluminumDREW Women's Dri-Lex ATHLETIC SHOES ~ White ~ 14497-22 ~ Size US 7W , Allbirds Womens Wool Loungers Casual Comfort Fashion Loafer ShoesWomens Skechers Flex Appeal 2.0 Estates Lightweight Memory Foam Trainers , Converse Chuck Taylor All Star Women's Shoreline Slip-On Sneaker Navy SIZE 7Reebok Classic Nylon Slim Core Women's Casual Retro Trainers Grey , NEW Womens DUNHAM 910 BR Brown Suede Slip On Outdoor Sneakers ShoesWomen's Rainbow Sandal Single Layer Premier with Arch Sierra Brown 301ALTS-SRBR ,
"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."