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.SODA Classic Elastic Panel on stitched fashion sneaker , Vince Camuto Womens Hadia Metallic D'Orsay Flats Shoes 6 Medium (B,M) BHFO 4061 , ARRAY Womens Freedom Leather Square Toe Loafers, White, Size 9.0 j5cn , Women's Privo by Clarks 76197 Ballet Flats Shoes Sz 7M Black Patent Leather AA14British Sz35-43 Womens Pointed Toe Tassel Loafers Shiny Low Chunky Casual Shoes , Womens AK Anne Klein Reptile Metal Bit Drivers 7.5 M Comfort Leather Flatssz 11 / 42 TS TAKING SHAPE Kira Sandals super-comfy wide shoes bling NIB rp$120!Clarks Artisan Cap Toe Elastic Patent Leather Ballet Flats Black Womens Shoe 7Josef Seibel Nora 01, sac à bride femme - Noir - Noir, 37 EUStuart Weitzman Black lacquer Ballet Girl Ballerina Flats Size 2 , Easy Street Women's Genesis Flat, Tobacco, 9.5 W US , Newbark 'Jacks' Saffron Velvet Loafers Shoes Sz 7.5 Slip On Burnt Orange $460GENTLE SOULS Size 10 NATALIE Demi Taupe Leather Ballet Flats Shoes , Reebok Yourflex #V72488 Womens Sz 6.5 Shoes Black and Wine LADIES GREAT SHAPE ** , Women's Nike TR 6 Running Shoes Size 9.5 Black Metallic Red Bronze 833413 005 , Wild Black White Men's Slippers Non-slip Light Beach Casual Home Bathroom Shoes , Sketchers Sport 22478 Breath Easy Running Women's Shoes Size 10 M , New Balance Training Sneakers Shoes Women Size 8.5 E White Blue WX623W Wide , Women's Woman Size 6 Converse Shoe Practical And Economical Athletic Shoes , Women's TROUVE-Women’s Shoes-Black-Flats-Elastic Slingback-Closed Toe-Leather Upper-8M Online Outlet Store FlatsPONY SHE RUN 78 LOW CHEVRON 1804 SNEAKERS WOMEN SHOES BLACK/PINK SIZE 10 NEW , NIKE AIR MAX THEA WOMENS SHOES ASST SIZES NEW IN BOX 599409 410 , Women's Adidas Cloudfoam Racer TR - Purple - Width: med - RunningNike Flex 2016 RN (GS) Girls Youth 834281 006 Sz 4-7 Fast Shipping K S , Brooks Glycerin 15 Navy/Purple Running Shoes Women's US 7.5 Wide (A3,13)Merrell Women's Tahr Waterproof Hiking Shoe Beetred/Vivacious Size 8M Select DryEtnies Regiment Skyline Collection Green Sneaker Boot, Size W 9.5. NWOB , Merrell Bare Access Arc 4 Women's US 10 Black/Teal Trail Running Shoe TrainerThalia Sodi Womens Azar Fabric Hight Top Zipper Fashion, Taupe, Size 9.0 XRzkNew Balance Womens - Thunder/Black/AlphaPink Running Shoes Size 9 (C,D,W)
"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."