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.Paolo Corelli Women's Bronze Leather Slip On Moccasin Penny Loafers US Size 6 M , WOMENS PAPRIKA TAN SLIP ON LOAFER WITH HORSE BIT HARDWARE SIZE 5 1/2COLDWATER CREEK Wedges Mary Janes Ballet Flats Clogs Loafers Womens Shoes Sz 8 , BASS Helena Womens Size 6.5 M Grey Blue Suede Leather Mules Shoes Slip On ClogsWomens Clarks Collection Navy Blue Slip On Loafer Size 9.5M Comfort Casual Work , Sanita Green Nursing Clog Loafer Work Shoe Womens 9-9.5/ 40 , STUBBS & WOOTTON Zebra Black Gray Loafer Slipper size 9.5 AA , Stuart Weitzman Ballet Flat Shoes 9M Textured Snakeskin Leather Buckle Round Toe , Excellent~ MEPHISTO Ecuba Black Air-Jet Slip-on Wedge Women's US 7 M , Crocs Women’s Walu II Canvas Loafers Sz 8 Hand Painted Brown Gold Triple comfort , Sperry Top Sider Boat Shoes Sz 9 Women Custom African Design YGI E8FitFlop F-Pop Ballerina Flats - Women's Size 40 / 9.5 Leopard Calf HairDeer Stags Dynasty Black Ladies Slip On Shoes, Size 8 M , New Balance Womens Walking Shoe SIze 7.5 B White 811 Made in USA DSL-2 , Brooks Adrenaline GTS 13 1201231B355 LIMITED EDN Size 9 Womens Shoes MOGOWomen's Size 7.5 Skechers Shapz Sport Shoe ~ Elastic Slip-On Closure ~ Brand NEW , SKECHERS ELITE MEMORY FOAM SHOES WOMENS SIZE 10Men Reef Voyage Flip Flop Sandal RF0A2YFQ Black 100% Authentic Brand New , Forever Collectibles NFL NEW Cleveland Browns Mens Moccasins Slippers , EASY SPIRIT - SEPIKET - WHITE LADIES SIZE 8M - OPEN BACK LIGHT ATHLETIC SHOEWomen's Puma Navy Blue Leather Sneakers 7M , SAUCONY COHESION 6 SZ 8 Gray Pink Sneakers Walking Running Work Shoes For Women , Women's Propet Women's Mary Jane Walker Special Buy FlatsWomens Nike AIR JORDAN 1 RETRO LOW NS NRG Shoes "Python" AJ6004 010 -Sz 9 -New , Ryka Studio D XT Athletic Shoes - Women's Size 9.5M - Silver/White , U.S. Polo Assn. Women's Geena-k Fashion Sneaker - Choose SZ/Color , Nike Flex 2016 RN 830751-800 Bright Mango White Women's Running Shoes NEW!Vans Sk8-Hi Slim ( Foil Metallic) Silver/White- Women's Size 5.5 , New Balance 620 Classics Walking Shoes CW6620BWK Blue/Neon 2V-10 Women's 8 BVans Women’s Asher Embossed Gray/true White Metalic Size 10
"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."