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.Brown Suede Leather Loafers Women's 7.5 B Clogs Slip on Shoes Lands End , Rieker Antistress Black Slip On Mules Womens Size 6,5 US 37 EUR Comfortable , WOMEN'S BRONZE BROWN BORN CASUAL SHOES SIZE 8 , CROCS Crocband Winter Flats Wo's 11 Brown Lined Insoles Casual Slip OnsRocket Dog Pewter Ballet Flats - Size 7 , Easy Spirit White Leather/Mesh Clogs 7 1/2M , woman's black HOT CAKES clogs shoesWomen's Rockport Walking Shoes Brown Suede Leather Oxford Size 7M , Unionbay Womens Round-toe Slip-on Loafer Flats , Womens Clarks 10 M Authentic Leather Black Slip On Mules Clogs Styled Shoes , Emporio Armani Silver Metallic Women' Size 37 Leather Ballerina Flat Shoes Italy , Nine West Women's Black Leonda Tassle Loafer Shoes Ret $99 New , Sanuk Donna Women's "Sidewalk Surfer" Lightweight Slip-OnFlats/ Various DesignsAnchor Costume Sailor Navy Anchor Blue Flat Shoes Size USA 6 In Stock , **Aeorosles Smart Move Flats - Women's Size 6W - Silver , U.S. Polo Assn. Mona Cross Strap Slip On Sneakers 010, Black Multi, 8.5 US , Dr. Doc Marten's Womens Shoes Leather SZ 9 M Clog/Slip-on DM's Mules Rubber Sole , Opening Ceremony Bordaux oxford shoes 37Women's Adidas Arianna Cloudfoam Running Shoes Blue BA8745Cabela's Outfitter Camo MicroDown Breathable Warm Cabin Hunting Slippers BootiesQupid Women's Narnia-01 Fashion Sneaker, Grey, Size 5.5 , Awesome Classic Keen Sport Sandals Womens Sz 7.5 - Free Shipping -Women's Converse Winter Sneakers Terrific Value Athletic Shoes , Women's Missimo Rhinestone Flats Hot Sale FlatsInov-8 Womens F-lite 235 Blue Pink Running Cross Training Athletic Shoes Size 9MBT Womens 10.5 US 7.5UK Fitness Mary Janes Gym Shoes White Walking SneakersCustom Fashion And Comfortable Women Boots Deer Martin Boots For Girl , K-Swiss Women's Court Cheswick S 95609-002 Black White Brand New in BoxPUMA Glyde Court Women's Sneakers Shoes Leather Dark Shadow Cabaret 354871 06On Cloud Womens Cloudrunner Red Running Shoes Size 7.5 (425145) ,
"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."