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.Palladium Kassel Leopard Elastic Strap Leather Ballet Flats SZ 38 | 7 , CITY SNEAKS FLOWERS SHOES WOMENS SIZE 8 , Cole Haan Orange Embossed Leather Mules Slides Women's us 38.5 , TRANPARENT POINTY SUEDED SANDAL WOMEN POINTER-153-05 QUPID BLACK NUBUCK , womens anne klein cailley multi colored leather skin print loafers shoes size 7Yosi Samra Ballet Flats Charcoal Snake Sz 5 NIBDana Davis Women's Brown Leather Slip-On Penny Loafers US Size 10Dansko Shoes Burgundy Clogs Mary Jane Women’s Sz. 41 , Skechers BOBS Womens Bobs Plush-Oh So Pitty Ballet Flat- Select SZ/Color.Cole Haan Men's Size 10B Two-Tone Vintage Leather Loafers Driving EC , Hot Chocolate Design Chocolaticas Habana Mary Jane Flats Womens Sz 38 US 8 NEW , TALBOTS "BONI" (MARIGOLD) LEATHER FLATS-SIZE 7M! NEW! FABULOUS! , Nine West Womens Smoak Suede Ballet Flat- Pick SZ/Color. , WOMAN'S 10 IVORY CREAM WHITE BEIGE SLIP ON SNEAKERS SHOES MESH PROPOSAL EUC ??Converse Sneakers Black Pink Size 2 Girls , NIKE Womens Flywire Sneakers,Running,Walking trainers, Black, US8, UK5.5, EUR39 , New Womens Pineapple Dance Casual Light Weight Hi Top Trainer Sport Running , Clarks Slip-On 71902 Red Leather Comfort Office Pumps Loafers Shoes Women's 6.5 , Skechers Sport Trail GrayBlue Walking Hiking Athletic Sneakers Womens Size 8 , BRAND NEW SM by STEVE MADDEN Sizes 7- 9M Velour Fashion Skate Tennis ShoesNIKE Son Of Force Mid Womens Sz 11 Rose Particle Blush Pink 616303-603 , New Balance W680RF3 Womens 680V3 Running Shoes- Choose SZ/Color.Savannah Cat Print Running Shoes For Women-Free Shipping , WOMENS DC UNILITE TRAINER RUNNING CROSS TRAINING DARK SHADOW TENNIS (01T)GRAY , Converse All Star Chuck Taylor Studs Eyerow High Top Sneakers / Women’s 9 , NEW! Asics T6D7N Women's Gel?Cumulus 18 Running Indigo Blue 6 101I paSuperga 2750 Cotu Classic Canvas Shoes in White Taupe, Black, Grey Blue & Green , Lucky Brand Women's Piyaa Slide Black Suede/Leather SandalsCHACO MADDIE LEAF GREEN TEXTILES & SUEDE LEATHER ATHLETIC SNEAKER SHOES--8.5 40NEW BALANCE WOMENS W690BL1 RUNNING SHOES ,
"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."