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.Jessica Simpson Ballet Flats Size 6 1/2 Monetah Gold Black Metallic BowMerrell Womens Brown Buck Suede Slip On Clogs Mules Jungle Slide 7 B M Sport , BORN Women 9 Leather Silver Bronze Gold Metallic Flower Ballet Flat Loafer Shoes , Women's Double-H Brown Leather Casual Mules US 7.5 MMerrell Encore Groove Floral Ginger Brown Leather Loafers J66394 Womens Size 7.5$195 size 5.5 Gentle Souls Erin Silver Leather Ballet Flat Loafers Womens shoes1.State Black Waylan Slip On Fashion Sneakers Womens Size US 6.5MCLARKS LADIES SUMMER SHOES 60807805 SZ 7MPreowned Cole Haan Black Velvet Flats Slippers excellent condition silk insole , Rieker Women's Slip-ons Ballerina Low Shoes Court Shoes Blue 537y5 NEWAL35 Dolores Ballet Flats 626, Gold, 6 US / 37 EU Display , LADIES SPOT ON GREY CANVAS SHOES "X0001" , Crocs Women's Carlie Cutout Clog - Choose SZ/ColorPAUL GREEN NICO Metallic Silver Moc Toe Loafer Rubber Sole AU 5 Women's US 7.5LA Gear Womens 8.5 Black Leather Sneakers ShoesCONVERSE CHUCK TAYLOR ALL STAR GREY FAUX FUR HI TOP SNEAKERS WOMEN'S 8Colorful Lady Women LightSport Shoes Sneakers Casual Running Shoes Outdoor Girls , Ahnu Women's Sugarpine Air Mesh Hiking Shoe - Choose SZ/ColorNew Foamtreads Canada Dinali Women Winter Shoes Slip Tribal Lined Leather Red 5 , KEEN Prescott 5440 brown leather sneakers Women's Shoes Size 8.5 , Women's Flat Nine West Gazookery Black/Black Large Assortment Flats , Skechers Grey Leather Rise Fit Wedge Metal Loop Rhinestones Wms Sneakers NWTNEW SAM EDELMAN WOMENS LEILA SNEAKERAltra Torin 3.5 Women's Black Zero Drop AFW1837F-02 Running Shoes Size US 8Skechers Women's Go Walk Lite Slip On Walking Shoe Blk/WHT 7 M USNike Women's ACORRA SUEDE Sneakerboots Dark Storm/Black 806977-210 a1New Women's Nike Free 5.0 TR FIT 4 PRT Training Shoes 629832302 Size 7.5Skechers Women Burst-Divergent 12730/Gry W/Air Cooled Memory Foam Running Shoes , Easy Spirit slip on sneakers canvas shoes size 8M Tan Tennis Walking Casual , Skechers Shape Ups Resalyte Womens Size 9.5 Black White 12471 ,
"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."