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.Women's Sperry Top-Sider Size 7.5M Boat Shoes Sneakers Brown Leather Casual A15Rajasthani Handmade Ethnic Sky Blue Ballerina Mirror Work Tradational MojariBLACK MERRELL SLIP ON CLOG SIZE 8 WOMEN'S SHOESAerosoles Size 7 1/2 Brown Suedy Women's Short Fur lined boots - Barely Worn , ARAVON WOMENS BLACK LEATHER ROCKER SOLE OXFORDS SIZE 7.5 B LANEY MODEL .. , Dansko Burgundy Leather Loafer Clog Moc Toe Mule Shoe Women's US 9.5 to 10 , SAS Tri-Pad Comfort Food Bed Shoes Womens 10 Loafers Black Moccasins Horsebit , New Super Cute Womens Embroidered Gray Leather Sketchers Sneakers Size 9.5Dolce Vita Pointy Toe Flats 7 Orange Gold Zipper DetailBamboo Nubuck Round Toe Ballet FlatWomen's DANSKO "Marcelle" Black Patent Leather Mary Jane Shoes 41 (10.5 US) , Kork-Ease Women's Maddison Black Mules 10MMocassins Confort BEBIBIRDBLUE Cuir Marron T 7 C / FR 40 TTBE , Aerosoles Tropical Floral Print Comfort Ballet Flat, 6 , Ryka Womens Size 6.5 Brown Sport Flats Mary Jane Slip Ons Walking shoe , Womens Reebok Super 2.0 Shoes Sz 8 Cross Training H2O Drain All Terrain CrossFit , MBT Womens Black Leather Rocker Toning Walking Shoes Size 9 , EXCELLENT! Asics GT-2000 T2K7N Running Shoes 8.5 Black/Blue/PinkWomen ECCO Performance Train Biom Natural Motion Athletic Sneaker Shoes 37 US 6INDIVI Shoes 974285 Silver 23.5ｃｍ , VANS Metallic Dots Slip-On Women | Rose / Spanish Villa (8F7MU5) , NEW BALANCE MADE2RUN Running Sneakers Shoe~KJ554SPY~Gray/Pink/Blue~Size 6.5New Women's NIKE AIR ZOOM 90 IT GOLF SHOES 844648 100 SIZE 8.5 , Nike Air Max 90 Premium Women's (Size 6.5) Metallic Mahogany White 896497-903 , New Balance Women's 574 Fresh Foam Shoes Blue with White , NEW! Womens Skechers RELAXED FIT: BIKERS - SATIN DREAM Taupe 49254 S51Adidas Sports Performance Volley Response Boost Womens Trainers B34724 D27New Balance 990 W990GL3 Gray Running Shoes Made In USA Women's Size 12 , Womens Pull on Fashion Athletics Running Casual Sneakers Mid Heels Shoes Size # , Converse X Missoni Chuck Taylor All Star Ox Sneaker ( Size Women's 6 ) ,
"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."