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.Naturalizer Womens Shoes, 6 M, Loafers Black Slip ons, Leather Mary Janes , Size 5 Womens Shoes Flats Ballet Aqua Mindy Gold Sparkle Costume Round ToeTerrific! Women's Brown Easy Spirit Leather Shoes, Sz 6 BSALE LADIES SPOT ON SLIP ON SHOE IN BLACK, BROWN AND NAVY F8531Spot On Ladies Tan Flat Leopard Print Shoe F8829 (R19B)Women's Ariat Black/ Brown Full Grain Leather Studded Clogs Women's US 9.5B , Easy Spirit Motion Oxfords- Women's Size 7.5 (4A), Wheatfield , US Indian Shoes Flip Flop Flat Shoes Indian Designer Shoes Punjabi Jutties DD892ROXY - Women's Tan Faux Fur Lined Slip On Clogs - SIZE 7 , Women's Pink Glitter Sperry Top-Sider Boat Shoes Size 6.5 M , Clarks Artsian Brown Leather Slide On Mules Women's Size 7.5 M 82715Women's Merrell Duet Groove Slip On Shoes Mules khaki Suede Size 6 , Convese Jack Pursel women's shoes, size 10, Gold, leatherSam Edelman Barbara Flats - Women's Size 8M - Hot PinkLUICHINY $84 BLACK SLIP ON FAUX LEATHER ATHLETIC Casual SHOES SNEAKERS SZ 6.5Cole Haan Grandos Womens Size 9.5 Blue Slip On Sneaker , NIKE WHITE WOMENS SIZE 9 1/2ASICS Women's GEL-Contend 2 Running Athletic Shoes White/Blue/Neon Green [156R]New! Mizuno Womens Wave Rider 17 Running ShoesJ1G D140308 White/Purple 177DCircua by Sam Edelman Carmela Pom Ball Fashion Sneakers, Cranberry, 8 US / 38 EU , New! Women's Skechers 12418 Empire Sharp Thinking Walking Sneaker - Blk/Char L12 , Womens Nike Free TR 7 MTLC Running Training Shoes Black Silver Grey 922844 001 , Vans Off the Wall Womens Prairie Chukka Perfed Black Suede Shoes 8 RARE , NEW Reebok DMX Lite Prime AR0114 Womens Shoes Trainers Sneakers SALE , NEW adidas snova glide 5 W - Running, Cross Training (Women's Multiple Sizes)Nike Air Jordan 2006 Retro VII 7 White Black Yellow Womens Size 11 313358-172Nike Wmns Roshe LD-1000 ONE / KJCRD / NSW Womens Running Shoes Sneakers Pick 1 , NIKE LUNARTEMPO SZ: WMNS 5.5 (705462 102) , New Nike Women's Air Force 1 Hi PRM Basketball Shoe Tan Silver 654440 002 Size 6NIKE WMNS BLAZER MID '09 ND ATHLETIC FASHION SNEAKERS ,
"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."