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.NEW Womens SODA OBJECT TAN Fashion Slip On Loafers PADDED Footbed Shoe SZ 8 , Patagonia Rossi Great Pink Advocate Mary Jane Ballet Flats 11Earth Origins Size 8 Flats RedNew With Box Womens Naturalizer Viva Ivory NIB 10 M Dress ShoeNaturalizer Womens Manor Fabric Closed Toe Slide Flats, Silver, Size 8.0 PWA0 , Keds Women's Champion CVO Seasonals Oxford, Slate Grey (WF51830)Stuart Weitzman 'Dotsalot" orange suede gold studded ballet flats 9M 4940 , Sole/society Ananda sandals Leather Knotted Flat French Taupe Flats 8 M $84.95 , Steve Madden Size 10 Beige Flats Sandals New Womens ShoesVionic Womens 9 M Ashby Driving Moc Loafers Leather Shoes Natural Snake FlatsNWT Sanuk FOLKLORE Off White Multi Color Canvas Flats Shoes Womens 9 M , G.H. Bass & Co. Westlyn Weejuns Loafer - Women's Size 9M Navy/Burgundy , SKETCHERS SHAPE UP TONERS Black Athletic Walking Sneaker Shoes Women’s US Size 9 , Smilun Lady¡¯s Ballet Flats Round Toe Ankle Strap Bowknot , Rockport Womens Sidewalk Expressions Sneakers 6.5 USNike Shox Black and Silver High tops Basketball Size Women's 7.5 Youth 6.5 , Hot Sale Womens Shoes Breathable Mesh Sneakers Wedge Hidden Sport Sandals BootsTony Little Cheeks Purple Mesh Easy Shapers Fit Body Trainer Sneakers 8 SALEReebok Women's Print Athlux Shatr Running Shoes Sneakers Black/Purplewomens asics running shoes size 10 Gel-fluxNike Womens Free TR Fit Size 8.5 , Bzees Cloud Technology Grey Floral Ruby Slip-on Skimmer Shoe 8.5 Sale , Saucony Womens S15333-18 Navy Blue Running Shoes Size 9.5 (2244)Women's Asics In Many Styles Athletic ShoesAmerican Foxhound Print Slip Ons For Women- Express Shipping??New Balance Women's 990 W990KM4 Komen Pink Ribbon Running Shoes Size 9 B , NEW BALANCE Womens so 11 Wide Black WW840BK Walk Training Athletic Shoes TJ-1062 , Palladium Women's Aventure Textile Ankle-High Fashion SneakerMERRELL Women 8.5 M Gray Blue Siren Edge Hiker Shoes Sneakers Vibram Sole J35516 , Women Skechers Originals OG 82 Spring Fling 145/Navy Blue Air-Cooled Memory Foam
"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."