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.Sperry Top-Sider Women's Mallard Blue Plaid Shoe 6MBass Rachel Antonoff Lewis heel floral oxfords white sz 7M in box retail $139 , Chaco Zaagh Black leather loafer shoes Womens Size 6 US 37 EU Vibram solesRalph Lauren Womens Brown Leather w/fabric Slip-on Pump Shoes Size 8M , Trotters Womens Sz 7N Black Loafers Slip On Woven Comfort Work CareerLands End Womens Flat Tailored Terrain Ballet Shoe Plaid Suede Leather Size 9 MClarks Women's Size 8 Distressed Leather Shoes Brown Mary Janes (S1)Butterfly Twists GIGI Ladies Fold Up Ballet Flats Shoes BLACK SNAKE 7 M (38) NIB$100 Vivobarefoot Womens Penny Moc Toe Flat Shoes, Black, 39 EU / 8 US , Women's Tsonga Bumba Chocolate Brown Moccasins US Size 7 B M , Sanuk Donna Chill Cord Black Women's Shoes Slip On Loafer 1099971Loafer Nine West Xcept 2 Dark Grey Multi FabricNew Women's Skechers 33954 Bobs Luxe Stained Glass Flats - Black Size 6.5 (L19)new balance women shoes size 7.5 , Calvin Klein Womens LAVIDA PEBBLE GRAIN Leather Closed Toe CLAY Size 8.0 grZc , Top Mens Handmade leather slippers,mules, sandals US 6,5-13, 39-47 (Hausschuhe)Saucony Original DXN Trainer Women's Running Shoes Size 9.5 S60124-40 GRNWomen's Merrell Avian Light Ventillator Waterproof shoes size 7Women Vans Old Skool - Authentic - SK8-HI Skateboarding Shoes Sneaker All SizesWomens Adidas Ultra Boost BY1900 size 10.5A472G Nike Women's Lunarepic Low Flyknit 2 863780-405 Size 11 NEW Retail $160 , Womens Hush Puppies 10EW Power Walker II White Leather Extra Wide New Box , adidas Originals ZX Flux womens size 6.5 , WMNS NIKE SHOE FREE TRAINER 7.0 IV 354175-071 ANTHRCT ZTRN WD PNK BLTC BL SZ 6Bzees Cloud Technology Black Watercolor Glee Slip on Sporty Shoe 9 New , Sz 8.5 NIKE ZOOM Track Field Womens Distance Racing Black VOLT Purple 553074 075Merrell Womens - Gray Trail / Hiking Shoes Size 9.5 (346508)John Varvatos Womens White Fashion Shoes Size 9 (347791)HOKA ONE ONE Women's ROCKET LD Track Running shoe Cyan Blue White Shoes Training , Women's Skechers Street Utopia Basic Canvas 785/BLK Black/ White Brand 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."