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 Fast-1 Brown Leather Suede Half Shoes Slip Ons Sz 7 1/2 M NewSperry Top Sider 9298694 Women's Pink Textile Moccasin Boat Shoe Sneakers Size 6 , Rockport Womens Brown Leather Slip On Flats Moc Penny Loafers 7.5W EUC , Nicole simpson Black Faux Suede Ballet Flats- Sz 7.5STUART WEITZMAN designer black suede slip on flats/loafers, sz. 7 1/2 NarrowNEW WOMENS LADIES SHINY COMFY PLAIN RUBBER SLIDER FLATS SHOES SLIDES SLIPPERS SI , women vince camuto loafers size 6.5. Patent w/chrome box bowWomen Shoes Indian Handmade Jutti Wedding Mojari Pointy Flats US 5-8.5Salvatore Ferragamo Black Patent Leather Flat Loafer ITALY size 10 AAAAnne Klein Womens Yophinep Shoe- Pick SZ/Color. , excellent MOUNTREK ANNA brown leather slip on comfort toggle loafers 6.5 , Bernice Spring Step L'Artiste Collection Women's Sandals Camel Multi US 7 , DANSKO Jute Pro Multicolor Green Blue Striped Clogs Womens Shoes 39 8.5 9 MINTHUSH PUPPIES "G-LIGHT" LEATHER SHOES stone WOMEN US 6 medium NEW , Clarks Muckers Womens Shoe Size 6 Brown Suede Leather Waterproof MoccasinsLucky Brand Flats SZ 7.5 US Women’s “Plush” Metallic Pink$85 New Balance Women's Silver Blue WW877SB Walking Sneaker Shoes Sz 9.5 Narrow , Casual Womens Canvas High Top Sneaker Sports Athletic Summer Shoes College NewTEVA Women's Athletic Shoes sz 5 Walking Trail Sport Gray Green Tan BungeeIMNYC Isaac Mizrahi Womens Kimberly B/W Fashion Sneakers 7 Medium (B,M) 1679 , Fancy Jessica Simpson Women's Fitt Walking Shoe, Shooting Star, Size 7.5 , Womens Basketball Athletic Shoes High top Training Sports Shock Absorb SneakersNike Blazer Mid Blue White Shoes Youth Size 7 Women’s Size 8.5 NWT , Nike Airmax Polarized Pink/Silver Suze 11 , Size 7 Women's Dr. Scholl's Persue Walking Shoe Memory Foam Cool Fit , SKECHERS Memory F Athletics Women’s Shoes, Navy/Gray Size 6 .......S31 , Skechers Gratis In Motion Black Lightweight Fashion Sneakers Shoes Women's 8 , New Balance 615 Walking Shoes Susan G Komen White Pink Silver US 8.5B , Dr. Scholl's Wander Up Slip On Sneakers, Coconut, 6.5 US / 36.5 EUAdidas Womens - White Fashion Shoes Size 5.5 (352776) ,
"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."