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.Women Merrel OrthoLite Aircushion Mesh Mary Jane Shoes US Size 8 , Ballet Flats Fergalicious Taupe Neubuck Uppers Flat Shoes by Fergie Size 6 NWOBJ Slides Rileyy Tan Perforated Suede Espadrille Sneaker (size 7.5M) , Klogs Missy Womens Clogs Shoes Display Model Leather Black Oil 9.5 M , Clarks Everlay Dairyn Slip-On Loafer - Women's Size 6.5W Black , ICON Los Angeles Gustav Klimt LEATHER "Kis" Moccasins SHOES 7.5 made in USA , ZARA BLACK FLAT BALLERINAS SHOES SIZE UK5/EUR38/US7.5Aerosoles Womens Traveler Flat Shoe Black & White Fabric Size 8 M US , New Womens Anthracite Isola Ladora Slide On Shoes, Size 6 MNIKE Free Fit 2 Running Women's shoes Size 8.5 pinkSteve Madden Womens Bertie-F Gray Fashion Sneakers 11 Medium (B,M) BHFO 5560NIKE SWOOSH Women’s High Top Size 6.5 Plum Purple And Light Purple Pearlized NewWomens Lolita Ankle Cross Strappy low heel Oxford Mary Janes bowknot shoesTORY BURCH Striped Elastic Espadrille Awning Size 10 Green CreamBALDI LONDON WINNY WHITE WOMEN TENNIS SHOE SIZE 40ZUMBA Women's ZUMBA Impact Max Shoes Size 9.5U.S. Polo Assn. Isabel Athletic Shoes - Women's Size 7.5 M, Black/Fuchsia 666 , Women's Sperry Nahla Sand Woven 10M Serviceable Flats , Women's Pilar Abril Leather Fringe Loafers New Style FlatsNike Lunar Control Vapor Women's Size 8.5 Medium Width Golf Shoes 849979-400New Womens Nike Flex Supreme TR 5 Athletic Shoe 852467-100 White/Silver 7.5 NIB , Converse Chuck Taylor Hi-Top Navy Womens Trainers Sneakers , Mizuno Women's Wave Catalyst Running Shoe, Atomic Blue/White, 7.5 B USNIKE Hyperdiamond 2 Keystone 856434-016 BLACK Womens Size 9 New Cleats Softball , Womens Size 9.5 White Silver Nike Shox NZ Running Training Sneakers 366571-111 , Women's Skechers GOwalk Sport Active Walking Sneaker 14138/BKAQ Black/Aqua New , SKECHERS Women's Black Multi GOGA MAX Performance Sneakers SZ 8.5 MSRP $60Topo Athletic Ultrafly Women's Ice/Red Road-Running Shoes 4.5M , Reebok Print Smooth Ultraknit Grey/Mist-White-Coal-Pewter BD4538 Women's SZ 9 , NEW WITH BOX NIKE WOMEN'S FLEX ADAPT TR TRAINING SHOES 831579 006 SIZE 8
"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."