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.B.O.C. Born Concepts Red Shiny Slip On Mules Clogs Shoes Size 6.5Easy Spirit Women's Esap1 Oxford, White Leather, 9.5 N USWomen's Dr Martens Buckle Slip On 2A87 Black Size 5 EUC , SPERRY TOP-SIDER Women's Boat Shoes Bahama Fog Leopard SIZE 5.5MKlogs Sadie Womens Clogs Shoes Display Model Polyurethane Navy 7 MNew Women's Pointy Toe Silp On Flat Leather Sweet Girl Loafers Spring Shoes03-49 Weejuns G.H. Bass & Co. Wynn Natural Sole Mule SIZE 7MEARTH Pewter Leather BELLWETHER Ballet Flats 6.5 BTORY BURCH REVA SIZE US 7M PATENT LEATHER BLACK LOGO BALLET FLATS A6 , LKNW Black BIALA Leather Ballet Flats Shoes Square Toe Stretch 7.5 ITALYZ58 Eileen Fisher Oath Earth Nubuck Leather Weaved Sneakers Women's Sz 11 M , Talbots Brown Reptile Textured Loafers Slip On Shoes Women's Size 6.5 USSaucony Grid Cohesion 10 Athletic Shoes - Women's Size 11, Grey/Mint 041Nike Prep Premium Sz 7.5 Brown Floral Leather Dance Yoga Fitness Shoes 316545 , Funtasma Women's Cthulhu 299 Brown Velvet/Bronze PU Size 6 MBaskets basses PEPE JEANS Sutton Or PLS30550 Nouvelle collection , Puma Sky Point Low - Black - Womens , Clarks 33446 Wave Perforated Driving Fashion Oxford Sneakers Women's US 8MSkechers Womens Bikers-Undergrad Chelsea Boot- Select SZ/Color.Women's Puma Cell Riaz Women's Sneaker Fast Shipping Athletic Shoes , A795G Nike Women's Air Huarache Run 634835-027 Size 6 New Retail $110 , Womens ASICS GEL-FIT SANA Black White Fitness Trainers S465N 9001 RRP .99New Balance 990 Pink Gray Sport Running Training Shoes Women's Size 7.5 D , New Balance Women's W580LG5 Running Shoe Black 6 M US , NEW WOMEN VANS AUTHENTIC LO PRO BLACK/ WHITE Free ShippingAbeo Lite Spring Black Mary Jane Athletic Adjustable Comfort Shoe Womens SIZE 11Nike Air Max Team ST Running Training White Navy Blue Sneakers Shoes Womens 6.5 , New Balance Cush+ Women's Training Sneaker Size 9 Grey , Puma Fierce evoKNIT Womens Slip On Training Athletic Fashion Sneaker ShoesConverse Chuck Taylor All Star Low Top Women Size 7 Polka Dot Sneakers 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."