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.J. Adams Round Toe Slip Ons-Women's size 7 White02-3529 Women's Sperry Seaside Perforated Sneaker Grey, Size 8MCrocs Kadee Ballet Shoes Flats Slip Resistant Work Rubber Womens Size 7 M BlackSKECHERS Mary Janes Shoes, 9.5 M, BLACK SUEDE BLACK CANVAS Loafers , LARKSPUR COLLECTION Needlepoint Ivory Dragonfly Sildes Mules Size Small 6.5-7M , LANDSEND WOMEN LOAFERS US SIZE 8 M SOLID GREEN LEATHER MADE IN ITALY. , WOMEN'S SUEDE COMFORT MAVENS BY MERCY FLATS SZ / 8 1/2 , Women's Crocs 14391 Size 6 Loafers Flats Shoes Beige Fabric Slip On K1 , Abound Kiley Flat - Blush Faux Leather Size 7.5 , SAS Free Time Women's 9.5M Tripad Comfort Shoes BoneClarks Brown Leather Mules Slip On Shoes-Womens-Sz 12N EXCELLENT! , Disney Shoes Donald & Daisy Duck Velvet Rhinestone SZ 6.5/7Dr. Comfort Betsy Black Leather Diabetic Mary Jane Shoes Womens Size 7X$120 Attilio Giusti Leombruni “Bijoux” Womens Sz 11 Black Cap Toe Ballet Flats� , $70 AEROSOLES WOMENS LOVE BUG SLIP ON LOAFERS BRAND NEW , Steve Madden Womens Haanna Pointed Toe Ballet Flats, Glitter Multi, Size 6.0 WMvReebok Women's Pheehan Run Wide Blue Silver Teal White Running Sneakers sz 7.5Asics GT-2000 Running Athletic Shoes Women’s 9Steve Madden Kandi Mule sizes 7.5, 8.5Tretorn Women's US 8.5 Nylite Tournament T56 White Canvas , Nike Cortez. White w/Light Blue Bubble Swoosh Women's Size 10Sam Edelman Women's Celina Platform Natural/Black Size 9.5 , Women's New Balance 1123 running shoes sneakers size 6 DNike Dunk Low Brown Map Youth 5.5Skechers Shape Ups Womens Size 8.5 Black White Toning Exercise Sneakers ShoeWomen's JANA Escarpin 22300-24 Gris Characteristical FlatsNike WMNS Blazer Mid PRM Hi Top Trainers Shoes 403729 105 WHITE VOLT 7.5Attilio Giusti Leombruni Resort Leopard Print Fashion Sneakers sz: 38 / US 8Kelsi Dagger Brooklyn Women's Royce Sneaker, Black Perforated, Size 7.01970's CONVERSE All Star size us 5,5 M/7.5 W Made In USA ,
"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."