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.Ladies Ballerina Diamante Casual Pumps Womens Dolly Ballet Mesh Flat Party ShoesRajasthani Women Flats Sandals Ethnic Flip Flops Casual Shoes Us Flat SlippersWOMENS FLAT LOAFERS SMART BALLERINA TASSEL PUMP BROGUE OFFICE DOLLY SHOES , Women's Naot Black Leather Casual Mules US 5 , NEW Women’s Sakroots The Sak Ella Espradrille Flats Canvas Shoes Size 6 7 8 9Blue & White Check Fabric LL BEAN Low Slingback Shoes 9 MELITES by WALKING CRADLE Womens ALEX Sage Urban Leather Clogs Size US 11 MCole Haan 9.5 Green Slip On Shoes Women'sSoftspots 9 Brown Mary Jane Womens Shoes , Sofft 'Mytalini' Leopard Print Buckle Flats Sz 6 New , Doc Martens England 8954 Womens Size 5 UK/ US 7 Burgandy OxfordsVictoria Women Flats Oxfords Canvas Shoes VioletPUMA Women's Vikky Baja Blue White 362624 19 Size 6.5 Suede Shoes 5324 Skechers GO WALK 3 FITKNIT SLIP Black - Womens - Size 8 BSAUCONY WOMEN'S RIDE 7 ATHLETIC SHOES~ SIZE 8. jjASH Genial Bis Taupe Canvas Wedge Fashion Sneaker EUC , Womens Vince Bowen Black Suede Low Top Sneakers 8.5Women's Merrell Moab Ventillator hiking boots shoes size 6.5 , Dansko Elise Oxford Suede Sneaker Black & Blue Tennis Shoes Sz 37 6.5-7Women's MONITALY Shoes 767861 Brown 7 A Complete Range Of Specifications FlatsWomen's NEW..G.H.BASS & CO..7.5 M..EBBIE..BEIGE..SEA CROC... Discount Flats , Women's LADIES DR CRINGLES SHOES BEIGE Fine Workmanship Flats , Nike Blazer Low Russian Floral Pack Womens AJ1689-001 Black Red Shoes Size 8New Balance Women's Nubuck 247 Shoes Off White with Off WhiteReebok Zpump Fusion 2.5 WP Black White Blue Women Running Shoes Sneakers AR2819 , Nike Flex Trainer 7 Anthracite White Green 898479-003 Women's Training Gym Shoes , Inov8 Bare-XF 210 Barefoot Running Shoes Women's Size 7 BlackAsics Gel-Lyte Komachi Athletic Shoes - Women's Size 8.5, Birch , PUMA Women's Basket Classic Metal Sneaker,Black,7.5 B USWomen's Skechers Sneakers - Microburst-Supersonic - Black/Pink - 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."