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.Born Women Brown Leather Side Buckle Clogs Mules Shoe 9 / 40.5 Rivets , Orthaheel MYLA Mary Jane Flat Brown Leather Shoe Women's Sz 8.5 without InsolesGenuine SAS Handsewn Womens Tan Shoes Made In USA Size 5.5M EUC! , GoldToe Deep Sea Coral Woman' Flats Medium (10) , Aerosoles Womens You Betcha Pink Smoking Loafers Shoes 9 Medium (B,M) BHFO 2900GIORGIO ARMANI Black Cream Leather Classic Spectator Flat Sz 39 , Prada White Leather Quilted Mary Jane Sneakers/Shoes Size 36/6STONEFLY Absolute Comfort Leather Mary Jane Shoes Navy Blue 7.5 / 38 Italy , New Sperry Top-Sider Hailey White Canvas Boat shoe/ 9778242Frye 86288 Black and Oxblood Leather Womens 11 Oxfords Work Play , Nurture Claira Size 6 M Loafer Shoes Flat Gold Silver Champagne Slip OnMinnetonka Canvas Moccasins-Women's size 8 Blue , Antonio Melani Womens White Leather Loafers Driving Shoes Size 7.5Heavenly Soles Women's Wide E Fit Ballerina Shoes TW4 Grey Size UK:8E US:10E , Black And White Unisex Teen Junior Sneakers Size 6 “just be.....” , Vans Authentic (Della) Batik Yellow Casual Shoes WOMEN'S SIZE 5.5 , Burnetie Women's High Top Vintage , K-SWISS Women's Blue Aster Bachelor Button X Court Sneakers Low NEW Size 8 MNike Free 4.0 Women's Running Shoes - Gray/Aqua - Sz 7.5 , Aldo Womens Dorea Low Top Slip On Fashion Sneakers Silver Size 6.5 Yo6u , Women's Asics Dynaflyte Womens. Size 6 Clearance Price Athletic ShoesAdidas Springblade Drive Womens Style C75669, PinkNike Air Force 1 HI Premium Women's Shoes 654440 $130 , Mephisto Niro Allrounder 8 Black Suede Leather Gray Mary Jane ShoesVANS Sk8 Hi Slim (Gold Eyelets) Laurel Wreath/True White Green WOMEN'S 5ASICS Gel-Kayano 23 Runnnig Shoes-Women's size 7 BlueAdidas Zx Flux Smooth Women's Shoes Size 5.5Ryka Aurora Womens Sz 7 Winter Sneaker Boots Comfort Shoe Blue Water ResistantWomen's CONVERSE Black+Lime ALL STAR Double Tongue Sneakers Shoes 140062F NEWNike Free 5.0 Running Shoes Sneakers Sz 7.5 White Orange Teal Womens 1A1
"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."