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.Etienne Aigner Brown Bone Leather Loafers Shoes Size 6M New Without BoxNew Women's Glitter Rhinestone Ballerina Ballet Flats Size 6 - 10 , Stuart Weitzman Infant Pali Gaby Silver Ballet Flat 3M , Luxury Rebel Womens Sari Silver Ballet Flats Shoes 8 Medium (B,M) BHFO 8707Women's Pointed Toe Shoes Canvas Flats Adorned Ribbon BowClarks Bronze Cut Out Leather Shoes Women's Size 6.5 MECCO Light Loafer Womens EUR Size 39 / US 8 - 8.5 Black Bicycle Toe Slip On ShoeAerosoles Final Exam Slip On Shoes - Women's Size 10.5M Tan , ANN TAYLOR Tan Leather Capped Toes Ballet Flats Women's Size 6.5 M Made In ItalySteve Madden Karry Coral Red Suede Jeweled Loafer NEWKlogs Missy Womens Clog Shoes Display Model Olive Tooled 7 M , DEBUT women shoes sz 8.5 Europe 39 black leather S7063Ecco New Touch Ballerina Black Womens Shoes Size 7 M Flats MSRP $130French Sole NY Light Blue Cutout Flats NWOB Size 9.5M , HIPPIE LAUNDRY WOMENS PIPPA BURGUNDY SLIP ON SHOE A5136-31K SIZE 11 NEW IN BOXBCBG MAX AZRIA Stella Black Brown Driving Moc Ballet Flats Mud Guard Size 6 1/2BORN BLACK MARYJANE CLOGS WOMEN SIZE 6 M , Reebok DMX Wire Mens Shoe NIB/New Performance Trainers White/Gray/Blue Size 13Nike Free TR Fit 3 PRT 555159 015 Womens size 10.5 Training running Shoes , ** FOOT JOY ** White & Brown Great Cond Womens Golf Shoes Soft Spikes Size 5 M , White Mountain Womens Saint Closed Toe OxfordsLeifsdottir Anthropologie Lahja Ballerina Flat BROWN Black Patent Size 39Dr. Martens Women’s Gwen Black Low Sneaker Size 7 EUCNew Womens Skechers EZ Flex It Factor Shoes Style 22634 Size 6 Gray 79B pr , Classic New Balance *** Turquoise And Pink *** Size 5 Women’s ***New! Women's Naturalizer Junction Leather Sport Wedge Silver Shoes , Women's Shoes /converse Low-priced Athletic Shoes , NEW Womens Nike AIR MAX 90 2.0 ULTRA Breathe sz 5 SUNSET GLOW Purple ShoesVASQUE Womens Talus Trek Low Ultra-dry Nubuck Leather Blue Brown Hiking Shoes 9M , NIKE LIGHT BLUE GRAY LEATHER & CANVAS SNEAKERS SKATE TENNIS SHOES 8.5 US 40 EURO ,
"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."