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.LADIES ELLEMENNO SUEDE LEATHER BROWN WITH BUCKLE SIZE 10 M , Duck Head Size 7 1/2 WW Judy Shoes - Mahogany , Clarks Artisan Cap Toe Elastic Patent Leather Ballet Flats Black Womens Shoe 7 , roger vivier Style Bule Flat Diamond Glitter Shoes 7.5 Size 38Me Too Brown Leather Driving Loafers Shoes Estelle1 Womens Size 9MIsaac Mizrahi Faun Womens Brown/Natural Leather/Textile Ballet Flats size 8 , Womens Havaianas Slim Tropical Beach Summer Rubber Lightweight Flip Flop US 6-11 , Ballerine MAM'ZELLE chaussure plate femme sport mocassin sneaker CUIR.37 NEUF , White Leather Soludos Shoes Size 6NEW! Skechers Women's GOTRAIN HYPE Shoes Black L hz , RBX WOMEN'S SZ 7.0 M INFINITY MESH WOODLAND GREEN CAMO 'NEW'--D 2451BERNE MEV NEW YORK "RILEY" ATHLETIC SHOES Black WOMEN US 5 EURO 36 NEWSANITA PROFESSIONAL SIZE 37 BURGUNDY PATENT WOMEN'S MSRP 140Lauren Ralph Lauren womens CAITLYN platino metallic kidskin driving shoes 6 NEWNine West Women's Smoak Denim/Synthetic Ankle-High Flat Shoe , Asics Gel Pulse 2 Women's Size 9.5 Running Shoes Purple Grey D8 , Nike Dunk Low Cognac Sand-Drift Sienna Womens Athletic Shoes Size 8NEW Womens Jambu JBU Cordoba Black Wedge Clog Slip On Shoes Sz US 8M , Women's New Balance 574 Classic Sneakers Size 8.5 WL574WTA Gray Black Neon EUC , Women's New Balance Women's Wlrushv1 Sneaker Wear-resisting Athletic Shoes , Saucony Women's Guide ISO Running Shoe, SLA/Pea, 10.5 B US , NEW SCHOLL ORTHAHEEL DEVISE WOMENS COMFORTABLE SUPPORTIVE ACTIVE SHOES , Rottweiler On Deep Skyblue Print Running Shoes For Women- Free Shipping , Puma Fierce Metallic Silver Women Walking Shoes 5.5Fila Women's Memory Workshift Cross-Training Shoe,Black/Black/Black,6.5 M USNEW Wmn's SZ 7.5, SKECHERS Performance GOrun Forza 2 OMG - PNK/PRNT 2017LA MRTHN , NWT Fila Smokescreen Low Sneakers - WhiteAetrex Womens Female's Sneakers Xspress Fitness Runner 5.5MAsics Gel-Cumulus 16 White Black Hot Pink Running Shoes T489N Women's Size 9.5 , ETNIES Womens Skateboard Shoes SCOUT MT W'S BLACK
"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."