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.Ara Bel Bar Silver and Gold Metallic Ballet Flats Size 6 (8.5 US) , Dansko Burgandy Clog Size 39 Womens Shoe 2 1/2 inch heel Comfortable Pre-owned , BATA Women's Cassadee Black Slippers (5716172)Ladies Contrast Sole Tall Rubber Wellies Winter Snow Waterproof Boots All SizesClarks Bendables Womens Sz 8M Black Leather Mule Clog Slip On Shoes Buckle 83545ASGI LADIES BROWN SUEDE DRIVING LOAFERS SIZE 6.5 M , BLACK HOUSE WHITE MARKET Women US6.5M Black Leather Barcelona Flat Faux Fur , Hush Puppies HPO2 Black Leather Slip On Loafers Flats Size 9.5M Comfort , Steve Madden Ellias Women's Black Size 10 B , Women Loafers Suede Caramel (Beige) Sofft Payton 6US=4 Youth=37$110 , Sudini Lori Fashion Sneaker - Women's Size 7 Frappe , White Mountain Women's Finesse Flat Grey Suede 7M New / DisplayNew Balance 850 Womens Sz 8.5 Running Walking Sneakers Shoes White GGUC , CLEARANCE!!!! LEVI'S Women's Stan G Slip-On Sneakers in Black, Size US 6Sanita Patent Leather Clogs Size 37 US 6.5 N narrow plum colorAerosoles Women's Fun Times Slip-on Loafer, White Leather, 5.5 M USAsh Nak White Womens Shoes Size 8 M Flats MSRP $198 , Privo By Clarks 34736 Green Gray Slip On Hook Loop Casual Shoes Women's Size 7MDREAM PAIRS Men's Avalon Sheepskin Fur Mules Fluffy Comfy Slippers , RYKA Kailee Blue Cross Strap Sneaker Walking Shoe Womens Size US 6.5MSkechers Performance Go Walk Joy Slip On Shoes Womens Athletic Casual Shoes Sz 8 , New Balance Womens WZANTSI3 Running, Cross Training Shoes 5.5 Medium (B,M) 6455Skechers Womens Vaso-Bota Fashion Sneaker- Pick SZ/Color. , Skechers Flex Appeal 2.0 Womens 12756-BKAQ Black Aqua Training Shoes Size 8.5 , RYKA NITE RUN Womens Nite Running Shoe- Choose SZ/Color.New $80 Sam Edelman Womens "Nerah" Nautical Blue Lycra Slip On Sneaker 7.5Kenneth Cole Kam Gray Womens Shoes Size 11 M Fashion Sneakers MSRP $120Reebok Classic Freestyle Metallic Silver Leather Size 8 New In Box! Orig $85Skechers Bright Idea Easy Going Slip On Sneakers Womens Size 8 Black KnitConverse Chuck Taylor All Star Ox Women's Sneakers Trainers Low Shoes Chucks ,
"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."