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 Women Casual Faux Leather Ballet Flat Shoes Size 6 - 10, (Fuchsia Color)SPERRY Top Sider Women Slip-on Shoe Grey Leather/fabric Rubber Sole Sz. 8Clarks Clog Women size 8 Mauve , womens g.h. bass & co blue slip on rain shoes size 6 , BORN Size 7.5 Black Leather Pointed Ballet Flats Shoes 7 1/2 , Wanted Arion Womens Silver Ballet Flat shoes 7.5MBorn Slip On Loafer Shoes Womens 7 M 38 Brown Leather Casual Plain Toe W8814Skechers Shape Ups Women's size 9.5 Pre-Owned walking shoes , Gold Shiny Womens Chic Glitter Slip on Loafer Boat Oxfords Shoes Flat Hot Salewomens casual soft low heel pointed toe slip on loafers shoes bowknot popularLucky Women's LK-BYLANDO Ballet Flat RED STONE , Katy Perry The Harra Ballet Flat Ivory Size 6.5 MConverse Womens Size 10 Charcoal Gray Shoreline Slip On SneakersNew Women's Puma Basket Platform Metallic Shoes 36616904 White-Lilac-Snow W24 dcWomen's nike Alvord 10 size 8.EASY SPIRIT ESFELIDIA SIZE 7.5M WOMENS NEW PEWTER BLACK WALKING SHOES , Women's Slip On Sneaker Mesh Loafer Casual Beach Street Sports Walking Shoes , Sanuk Women's Maisie Sneaker, Natural, 10 M USPleaser Pink Label Women's Fab 422 Open-Toe Pump Red Satin Pumps , TOMMY HILFIGER FASHION SNEAKERS NEVER MISS SIZE-9WOMEN'S HEXAFFECT FIRE 2.0 SIZE 8USSaucony Zealot Running Shoes BabyBlue/Lime Women's US 11.5 (C2,9) , Converse CTAS LOOP OX IVORY CREAM SIZE: 10 WOMENS Rose Gold Snake Print NIBSaucony Triumph ISO 2 Running Shoes-Women's size 7 SilverNike Free Run+ 2 EXT Womens 536746 400 Trainers CLEARANCENIB Merrell Mesh Moc Size 10 Blue SurfCONVERSE WOMEN SHOES CHUCK TAYLOR ALL STAR FLORAL BREAKPOINT OX SNEAKERS Size 5 , Saucony Lancer 2 Running Shoes, Women's Size 7.5 Teal/Orange , Puma Basket Heart Patent Leather Womens Sneakers BLACK size 8.5 ,
"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."