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.CUTE COMFY Women's Brown Suede Leather Nickels Clogs Fur Trim Shoes Slip On 11 , Indian Handmade Ethnic Blue & Yellow Ballerina Mirror Work Traditional MojariMINNETONKA MOCCASINS Women's Shoes Kilty Size 9.5 Light Brown Suede Rubber Soles , Clarks Artisan Brown Soft Leather Slip On Mule Clogs Shoes womens 9 Woven BuckleDeerstags Whenever Slip on Slipper - Women's Size 6M BrownWomen's~CROCS~Animal Prints Animal Prints~LOGO~Flats Shoes size 6 M~Super CUTE!Old Beijing Cloth Embroidered Shoes Flax red , Lifestride- Fantell Flats, Women's Size 10 M, NavyWomens Shoes Mary Jane OTBT Springfield Gunmetal Metallic Size 6.5 , Naturalizer Heaven Ivory Tan Patent Leather Buckled Flats Loafers Shoes Size 6.5 , Bass Weejuns Womens Wayfarer Leather Penny Loafer Shoes Beige Size 6 , Calvin Klein New With Defects Womens Pritah Gray Black Flats Shoes 7.5 Medium , Ladies Easy B Black/Navy Leather Shoes FifeTrotters Liz Loafers - Women's Size 6 M, Navy , The North Face Women's Ultra 109 GTX Hiking Shoe Steeple Grey/Balsam Blue 7.5M , SANUK WILLOW PILLOW BLACK MULTI CHEVRON COLOR SIDEWALK SURFER SLIPPERS SIZE 8 US , Mini Melissa Kids' Ultragirl Sweet III Black Size 3 Medium US Little Kid AMcm , Easy Street Women's Laurel Flat, Black Leather/Suede Leather, 6 M US , LADIES HI-TEC WHITE/VIOLET TRAINERS STYLE SQUASH CLASSICWomens Converse Chuck Taylor All Star Shoes Sz 7 Womens EucSkechers Women's Go Flex Max Loafer Navy Size 5.0 , Women's womens nike free sneakers We Have Won Praise From Customers Athletic ShoesWomen's Skechers Women Flats 8.5 Genuine Flats , Steve Madden GRAP01S1 Womens Graphic Fashion Sneaker- Choose SZ/Color. , KEEN Women's Atlanta Cool Gargoyle Steel Toe Work Shoes 7.5MPainted Labrador Print (Black/White) Running Shoes For Women-Free Shipping , Skechers Performance Women's Go Mini Flex Galore - Choose SZ/ColorSalomon Women's Sonic Pro Running Shoes 379173 Purple/Green, Pre-OwnedSkechers Women's Endeavor-Venturer Taupe Fashion Sneaker - Size 7 / 8Zee Alexis Womens Danielle Athletic Shoes Black Teal Multi 8.5 M ,
"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."