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.BLACK BORN CLOGS SHOES SLIDES Pebbled Leather Upper Women's USA 9/ , Bandolino Womens Elan Beige Ballet Flats Shoes 6.5 Medium (B,M) BHFO 6817Steve Madden Excuse Women's Loafer SZ 9.5MERRELL Women's 'Barrado Dark Brown' Zip Front Zipper SHOES/FLATS sz 9 MWomen's Sperry Top-Sider Size 7M Boat Shoes Gray Suede Casual Lightweight S4 , Diane Von Furstenberg Womens Dakar Black Ballet Flats 6 Medium (B,M) BHFO 9366WOMEN SHOES MEPHISTO LOAFERS Size US 6.5M BROWN SUEDE PORTUGAL , Andrew Geller Hanette Women's Red leather Ballet Flats US Size 8 M - A3900LFL by Lust for Life Women's Triplet Ballet Flat, Black, 9 Medium US , Clarks Wave Route Slip On Casual Shoes - Women's Size 6 M, BlackNew Sperry STS95714 Seaside Perf Leather Black Women's Boat Shoes 7, 9.5, 10Betsey Johnson Women's Solar Mule, Black/Multi, Size 6.0 H0S3Steven Comfort Lora Embroidered Sneaker Mule Open GRAY PEACOCK 8.5W , Jessica Simpson Womens neverly Fabric Closed Toe Ballet, Nude Blush, Size 8.5 sF , Vintage 90s Womens Tennis Shoes Size 10 M New in BoxChuck Taylor Pink Converse All Star Size 6 , Ryka Women's Faze Cross-Trainer Shoe, Black/Black, Size 5.0 , NEW BALANCE Women's "560 All Terrain" Grey/Pink Trail Shoes Size 8 , Nike Womens Lunar Converge White Running Shoes Size 10 (425269)Women's Nike Used Volleyball Shoe Cheap Athletic ShoesWomen's SPERRY Top-Sider Luna Silver New Excellent Quality Flats , Skechers Synergy 2.0 Scouted Athletic Women's Shoes Size 7Converse CTAS Lift Ripple Hi Black Natural Womens Canvas High-top TrainersNike Women's Mayfly Lite Pinnacle Running Shoe, Thunder Blue/Obsidian, 8 , Women's Air Jordan 1 Retro Low NS Basketball Shoe AH7232-623Women New Keen McKenzie II Water Shoe Sky Diver Plaza Taupe Sz 8.5NIKE INTERNATIONALIST Light Khaki Satin & Suede SNEAKERS Womens Size US 8NEW Womens Adidas CF Super Hoops Mid W High Tops Size 8 NEOVans Womens Size 8 Sk8 Crackle High Top Streetwear Sneakers , New Womens Skechers Go Flex Walk Shoes Style 14010 Size 8.5 Black 98o pr ,
"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."