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.1a BASS BROWN LEATHER LOAFERS WOMENS 6 M , Liz&Co Black Leather Clog Mule Slip-On Size 7 CallowayAntonio Melani Slip On Loafers Flats With Bow Bone Tan Leather Women's 10 Medium , Restricted Womens elsie Leather Closed Toe Oxfords, Black, Size 7.5 1l8iEasy Oriental Print Cloth Mary Janes--Size 10 , Birkenstock Boston Suede Taupe Shoes Womens Size 36 ClogsDonald J Pliner Women's 6M Lovage Gold Snakeskin Faux Slip-On MulesHAFLINGER Smoky Brown Suede WMN’S Size 9.5-10 NewNew Sperry Top Sider Bahama Black Sequin Boat Shoes Women's 8 MCOLE HAAN w N Air Technology Morgan Melon/Pink Smoking Loafer NEW Sz 5.5 , PAUL GREEN Tan Suede Women’s Loafers Size US 7.5$144 Excellent~ DREW Orchid Black Leather Cross-Strap Mary Jane Women's 11.5 M , Jessica Simpson JS-MIKAELA Womens Mikaela Ballet Flat- Choose SZ/Color.ASICS Women's Size 9 GEL CENTAURI Flash Yellow Blueberry Punch T3N6NDockers Mens House Slippers -Black- Brown- Grey Medium or Large New WB , Nike Rosherun Print Gray & Turf Orange 599432-800 Size 9 Womens Running Shoes , VANS New Rata Vulc SF Kassia Vault Lady's size 7 , CONVERSE HI TOP SNEAKERS SHOES WOMENS 7.5 ANIMAL PRINT , Nike Size 11.5 Women's Prime Hype DF 2016 Basketball Shoes Black White Silver , Athletech Snickers for girls size 3 1/2Women's FAGUO Cypress Bright White New Listing Athletic ShoesWomen's Womens~Heelys~Roller Shoes~Sneakers~Size 6~Skate~Girls~ Exquisite Athletic ShoesDC SHOES WO'S MAVEN WOMENS RUNNINGNIB Nike Dual Fusion X Womens Athletic Shoes Size 11 , VLADO ATLAS 2 W WOMENS SIZE 10 SHOES IG 1503 221 TEAL CUTE FASHION SNEAKERS NEWSaucony Women's Cohesion 11 Running Shoe , BROOKS GTS-16 Running Cross Training Shoes Size 8 , VANS SK8 Hi Slim Zip (Plaid Flannel) True White Black High Top WOMEN'S 10Women's Skechers Empress Fashion 100% Sneaker Shoe 23101 Color Black Brand NewVince Camuto 7.5 Sneaker Maroon Slip On Sneaker Note Barita Suede Women New
"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."