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.BZEES Twinkle Mary Janes Athleisure Grey & Navy Blue Arch Support Sz 9WSO STAR FISH BLUE Women NWOB Sandals Size 10M Blue , Womens Pointy Toe Flower Pattern Casual Slipper Oxford Style Flat Heel Shoes , Karen Scott Cadyy Women Flat (9.5M, Blue/White)SAS Leather Shoes Women's 7 1/2 WW Tan7 | Minnetonka Women Tan Suede Leather Thunderbird Hard Sole Moccasin ShoeDEMONIA EMILY-303 Platform Black & White Retro Goth Studded Saddle Shoes OxfordsClarks Everyday Women's loafers Black Leather size 8.5 M Slip On Shoes , SAS Tripad Comfort Walking Shoes - Black Leather ~ Women's Sz 10 N ~ Narrow , $145 VIA SPIGA BELOVED Red Zebra Designer Comfort Round Toe Ballet Flats 6.5BX770 J. K. ACID shoes silver paillettes women slip on , Fila 5HAW0000-162 women white Dynamic Landing System running sneakers size 9.5 , Naot Mary Jane Brown Leather Hi Heel Clogs US 6Columbia 10 M Red Suede Tennis Shoes Leather Fashion Sneakers Euro 40 NEWSaucony Womens Excursion TR8 Running Trail Shoes Sneakers Sz 6 f872 , Nike Huarache Womens Size 6.5 Gray Blue Green Big KidMerrell Castle Rock Azura Women's Waterproof Hiking Trail Shoes - US 8.5 () , Reef Low Top Gray Textile Sneakers Size US 8Nike "Sport Performance" black golf shoes, Women's 7 (eur 38) , Aerosoles Salt Water Gold Slip-On Sneakers Size 8M , Women's Munro Genuine Black Leather Loafers Wide Varieties FlatsQupid Women's Matthew-01 Fashion Sneaker - Choose SZ/ColorNew Size 10 Women’s Nike Air Max Sequent 3 Running Training 908993-011Salomon 643 Contagrip Nubuck Ankle Hiking Trail Ankle Boots Women's US 10NEW TEVA WOMENS FREEWHEEL SLUBBY CANVAS SNEAKERLucky Brand Women's Gallah Flat Sandal Sesame Leather Sandals , SKECHERS WOMEN'S INSIGHTS FLEX APPEAL 2.0, LIGHTWEIGHT WALKING COMFY SNEAKER , Skechers Work Women's Kincaid II Slip On Slip Resi - Choose SZ/color , New Nike Womens Free Tr Focus Flyknit Training Shoes 844817-302 Green glow Sz 9Brooks Ravenna 6 Size 8.5 Women's Running Shoes Comfort Quality ,
"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."