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.NEW Womens SODA OBJECT TAN Flats Slip On Loafers Dress Shoes SZ 8 , Womens Casual Shoes Ferragamo Flats Slip On Black Leather US Size 5 NarrowLOT OF 2 MUSHROOMS Comfort Loafers size 7W Exc 90% Condition BEIGE & GRAY shoesNew Women Fur Moccasin Warm Round Toe Flats Shoes Size 5-10J RENEE' LADIES DRESS SHOE PUMPS IVORY W/GOLD STUDS, GOLD SPIDERWEB TOE 6 M , Womens Boc Born Concepts Black Leather Clogs Size 8M With Buckle Heels Bootie , Elliot Lucca Women's Blue Leather Woven Slip On Summer Flats Size 8SAM EDELMAN CIRCUS BLACK LIZARD PATTERN WOMENS OXFORD SHOES SIZE 5.5M ON SALECOLE HAAN Women's Air Bria Black Shoes Patent Leather Toe 6.5 , Steve Madden Katie Metallic Navy Blue Embossed Smoking Loafer 8.5 Sale9 West Boat Shoes Womens Maureen Size 9N Kilty Tassel Mocs Summer -3088 , Adidas W Slides Sandales SZ 8 Voloossage Women AQ5907 Athletic Black, White NewYves Saint Laurent Sz 7.5 Brown Suede Pumps Crisscross Straps Low Heel Italy YSLBorn Slip-On Loafer Buckle Moccasins Brown Leather Comfort Shoes Women's Size 7 , Ipanema Women's Premium Love Knot Embellished Flip-Flops US 8MASICS SNEAKERS SHOES WOMENS 9.5 GEL E052Y RUNNING SHOES FREE SHIP!CUTE LIME GREEN SUEDE SNEAKERS TENNIS SHOES 7 GREAT CONDITION STEVE & BARRY'SWomen’s Nike Air Athletic Hiking Trail Running Shoes 9.5 , The North Face Litewave Explore Trail Running Sneaker Womans Sz 6.5 Pink & BlueMerrell All Out Burst Boulder Women's Running Shoes Brown Size 7.5(US)Brand New- Nike Womens Victoria NM 525322-605 Size 10Nike Dart 10 X Running Training Workout Blue Mesh Sneakers Shoes Womens 8.5 , Puma Women's Faas 350 S Running Shoe , Converse Size 7.5 DIGITAL FLORAL OX Canvas Fashion Sneakers New Womens Shoes , NIKE WOMENS LUNARSTELOS RUNNING SHOES , VANS New SK8-Hi Reissue DX California Souvenir Vault Lady size USA 7 , Kenneth Cole New York Kam Sneakers, Women's Size 9 M, BlushG by GUESS Otrend High Top Fashion Sneakers Black White 7.5 US , New Balance Women's Vazee Coast Running Shoe , 02-88 Brooks Glycerin 16 Women's Running Ebony/Green/Black SZ 9.5B
"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."