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.SPERRY TOP SIDER - Womens Blue Patchwork Plaid Fabric Boat Shoes, Sz 9 M , STARRY EYED TAUPE FAUX SNAKE LIGHT- UP LOAFERS, SZ 9, NEWBally Women's Shoes Flats Loafers, 5.5 B yellow leather Made In Italy Preowned , NEARLY NEW Forever21 Faux Suede Ankle-Strap Crisscross Straps Flats OLIVE Size 7Women's MBT Tan & Brown Leather Buckled Mary Jane Comfort Walking Shoe Sz 8.5MWanted Breakout Women US 10 Solid Black Oxford Blemish 2 11/16" High Heels 10943MIA BLING Bedazzle Buff Gold FLATS Shoe 7.5M Slip On NEW CLASSIC CHIC HOLIDAYLifeStride Women's Realize 2 Ballet Flat , BCBGeneration Womens Talia Leather Closed Toe Ankle Wrap, Shell/Shell, Size 9.5BJORNDAL Leather Clog Style Slip-ons - Women's Size 7.5 - Retro Floral Design! , COLE HAAN Size 9.5 Red Patent Suede Ballet Flats Shoes 9 1/2 , Pleaser Round Toe Foldable Flats W/ Bow Adult Women B. Pink Pat Shoes , MBT Mahuta Swiss Shoes Women's Fitness Walking Toning Sz 9-9.5 / 40 M , Skechers MJ Casual Shoes, Black/Silver with Strap, Women's US Size 9.5 , New Balance Women's W880SB4 Size 10.5 Running ShoesNew Balance 695 v2 Running Shoes Women Size 11 , Sneakers Femme ETNIES Czar 2 Mid Purple WhiteEasy Spirit Traveltime Women Round Toe Suede Pink Mules (7 M)Nike Air Max 90 GS Wolf Grey White Platinum 833412 016 Women's 7.5 Boy’s 6YNike LUNAREPIC FK SHIELD GYAKUSOU Women's Running Shoes 6 US , Puma Match Lo S Snake Women's ShoesSkechers Shape Ups X Wear Hyper Active Black Mary Jane Toning Shoes Women's 7.5MVans Womens Skate Shoes - Camden Stripe - (Snake) Natural, Ladies Trainers , Ryka Women's Slip On Sneakers Tennis Casual Shoes 8.5 Lightly Used EUCNIKE FLEX 2016 RN WOMENS SHOES ASSORTED SIZES BRAND NEW 830751 101 , Converse All Star Women's CT OX Floral Black/Multicolor Sneaker - Size 11/12 NWBPuma Basket Platform Glitter - Silver - WomensPUMA Women's Suede Remaster WN's Fashion Sneaker Black Black 8.5 M US , Puma Lab 2 Blue Khaki Green Sneakers Casual Tennis Shoes Womens 9.5 Med LeatherVionic Cypress Trail Walker woman grey/blue shoes Brand New ,
"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."