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.Hush Puppies Brown/Blue Leather Top Stitch Ballet Flats Slip On Women Shoes 11 NSo Women's Beige Patent Leather Round Toe Slip On Ballet Flats Size US 9 , Clarks (74516) Brown Leather Open Back Slip On Casual Shoe- Size 10 MSperry Top-Sider Black Leopard Gold Lacing Trim Boat Shoes Women Shoes 9.5 M EUCSAS Black Leather Mary Jane 6 N Narrow , nurture chestnut 40 9M womens ladies dark brown leather bow ballet flats , Natural Soul Naturalizer Fernanda Women Solid Brown Suede Mules Shoe size 8.5 M , Minnetonka Moccasin Women Size 6 Red Classic Kilt Suede Driving ShoesMERRELL womens black slide on mules moccasins shoes Primo Seam size 6.5 , Clarks Indigo Beige & Gold Leather Comfort Ballet Flats Size 7.5M , Nine West Womens Onika Leather Pointed Toe Ballet Flats, Blue, Size 9.5 , Alaia Tan Suede Ballet FlatsEUC Anthropologie MUSE women Neon Yellow SZ 38 leather FlatRyka Aries Athletic Memory Foam Sneakers Leather/Fabric Black/Blue Womens 6.5MCall It Spring Women Merwina Sneaker Hi Top Shoes 8 Black Suede Leather StuddedReebok Classic Leather sneaker White/Blue US 6.5 , Nike Free 5.0 Women's Running Shoes 642199-062 Sz 8 US , Easy Spirit Roadrun Athletic Sneaker - Women's Size 8.5M, White/Blue , MBT "Boost Rose" Womens Physiological Footwear White Walking Shoes Size 6Asics Gel Equation 7 Sz 11 Grey Pink Comfortable Running Sneaker Shoes For Women , Women's adidas Flashrunner Shoes Women's To Win A High Admiration And Is Widely Trusted At Home And Abroad Athletic Shoes , NIB Under Armour Micro G Assert 6 1266252-001 Black Pink White Womens Sz 6 6.510NIKE AIR MAX ZERO ESSENTIAL BLACK ATHLETIC RUNNING SHOES 6Y = Size 7.5 WOMENSNike Women's Air Tech Challenge II SE Athletic Sneakers Size 6.5 (857879-301)Nike Air Max Thea Mid Womens Lifestyle Boot 859550 002(Black) NEW Wmns Sz 8NEW BALANCE W630RB5 WIDE PINK BLACK W630RB5 WOMENS US SIZES , Womens Nike Free 5.0 TR FIT 4 PRT Running Shoes Size 7.5 Black White 629832 008 , Tretorn Womens NY Lite 12 Plus Black Fashion Sneakers 9 Medium (B,M) BHFO 6916Womens Nike Shox Reveal 3 gray/red running training shoes sz 9 , Luichiny Women's Tippy Toes Black Imi Suede/Imi Snake Size 10 M ,
"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."