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.Great Condition Clarks Artisan Sz8.5 Women’s Flats Beige & Black Patent LeatherAerosoles Shoes Ballet Flats Womens Brown Leather Slip On Buckle Detail Size 9Women's Wear Ever Mule Shoes - 6M , Womans Light Gray Loafers Size 9 Med Heart Cut-Outs On Soles Soft Spots? , Women's G.H. BASS CO Rain Shoes Low Ankle Black Size 7M , Women's Skechers Bobs Luxe Rain Dance moc style flats slip on sz 8.5 MTEMBA TAUPE LARSP65 Women's Shoes Size 7 M Leather Mephisto , Etienne Aigner Emory Loafers Cognac Brown Women’s Size 6 M Gold Metal Accent EUCBrighton Women's "Melisa" Dark Red Patent Leather Flats 10 M , Eastland Womens Leather Brown Clogs Slip Ons Caldora size 7 WideBelle Sigerson Morrison Women's Black Leather Slip On Ballet Flats US Size 10 , New Women Betani Abela-19 Pointy Toe Single Flower Instep Strap Flat MuleBrinley Co Womens Lena Pointed Toe Ballet Flats, Black, Size 9.0 Ua2d , BOBS from Skechers Womens High Jump-Urban Star Platform- Pick SZ/Color.Rockport Womens HW20 Gore Fabric Cap Toe Ballet FlatsMe Too Harlow 2 Women Tan Mary Janes US 8 M$219 Hunter Real Shearling Fur Lined Shoes Platform Clog Brown Shoe 10 NewRARES BASKETS COLLECTOR TOILE ARTENGO BLANCHES T 39 A ACH IMM FP RED MOND RELTod’s Women’s Snakers Black Leather Buckle Us 7 Eu 37.5 , Retro Womens Leather Slippers Chunky Heel Metal Decoe Single Shoes NewK-Swiss Women's Tubes Infinity CMF Sneaker, Highrise/White, Size 7.0Clarks Perforated Leather Ballet Flats Gracelin Lea Red 7.5M NEW A306040 , Anne Klein Zasa Slide Fashion Sneakers 480, White Multi, 9.5 USEasy Spirit Walking Shoes "HYPNOSISS" Taupe Leather Size 8 1/2 W , ladies sandals Kelsi womens ankle glitter diamante pencil heel open toe shoes , Skechers Go Walk 3 Walking Slip On Shoes Women’s Size 7.5, Black 1106 , Asics GT-1000 6 Running Shoes - Women's Size 10D, Grey/Flash Coral , NIKE WOMENS DUALTONE RACER SE SZ 8 MUSHROON WHITE GUM BROWN KHAKI 940418 200Nike Air Max 1 Ultra Moire Sneaker Shoes Women's Summit White / Racer Blue 7.5New Balance Women's WMD800V5 Track Shoes White/Purple Size 10 B(M) US **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."