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.Earth Women's Stratton Leather Loafers Slip-On Shoes in Black Size 6B , Clarks Medium Heel Clogs Black Leather Slides Womens Size 6 M , Hearsay Ladies Red Comfort Shoes Size 6Women’s Merrell Vibram Sports Shoes. Size 10 Grey, Lavender,.Dingo Fluchos Shoes 38 7.5 Black Loafers Moccasins Slip Slide On Cutout ShoesBorn Clogs Brown Leather Woven Mules Heels, womens Size 9 GUCWomens Clarks brown 6 M leather flats 71422 slip on loafers , Minnetonka Moccasins 533 - Women's Fringed Moccasin Loafers, Size 8Ecco Bluma Summer Ballerina Grey Women's Slip On Comfort Flats Size 36 / 5 - 5.5LifeStride Women's Ballad Slip-On Loafer, Brown, Size 6.0Steve Madden Women's Poppi Ankle-High Slip-On ShoesMARC BY MARC JACOBS PATENT LEATHER WEDGE THONG FLAT SANDAL SIZE 38BORN WOMEN'S W6133 BROWN LEATHER CLOGS MULES SIZE 10 US / 43 EURReebok Womens Classic White/White/White Fashion Shoes Size 10 (345294)GIRLY GIRL Keira Women sz 7 Turquoise Sneaker Shoes , Sam Edelman Leya Suede Pom Pom Sneakers, Women's Size 9.5 M, Black , Women's Olukai Miki Black Size 7 Running,Hiking,Water sport ShoesNew Mens ADIDAS AQUALETTE CF (CM7927) All Sz Adidas Beach SlippersPuma 5000m Womens sneaker Size 10 Baby Blue/Purple/White/Grey - RAREWomen's New Balance 409 Shoes Sneakers Size 9D Wide Walking White Blue Gray AC2New Balance 850 Women’s 10.5 2E Extra Wide Orange Blue Running Athletic ShoesConverse All Star Silver Snakeskin High Top Athletic Shoes Women's Size 8 , CONVERSE WOMEN'S CHUCK TAYLOR ALL STAR METALLIC RUBBER HI TOP LIGHT GOLD SZ 10 , New Balance WL220BG Sneaker Multi-Color Women's Shoes Size 9 M , Women's A'Rock Women's Richfield Orders Are Welcome Athletic ShoesDownunders Purple Running Insert Men's 11/ Women's 12 , Saucony Women's Omni 15 Running Shoes - Size 6, Grey/PinkASICS Womens Gel-Venture 5-W SilverGrey/Turquoise/LimePunch Running Shoes Size 7Brooks Ghost 10 Sneaker - Women's Size 9B GrayU.S. Polo Assn. Women's Cristal-j Flat - Choose SZ/Color ,
"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."