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.Merell Womens Slip on Flats Size US 10Sperry Top Sider Womens Beige Leather Flat Boat Shoes Loafers Slip On Size 7 M , NEW Women's Fringe Zip Round Toe Moccasin Flat & Wedge Boots Shoes Size 5.5 - 10 , Shellys London Womens Abeniel Canvas Round Toe Loafers Gray Size 9.0 mbgA , SO Women Summer Flat Plastic Sandals Bright Peach As-Is , Merrell Qform Ortholite Mary Jane Shoes Size 8.5 M BrownWomen's SAS Shoes Sneakers Size 6.5S Slim Beige Leather Wedge Hand Sewn USA J7 , Clarks Bendables Womens Brown Patent Croc Embossed Loafers Size US 9MNaturalizer Marianne Slip On Shoe - Women's Size 8M SilverNIB $100 Born LETITIA Tan Flats Shoes Womens 38 size 7 M , Dansko Women's Roxy Bordeaux Croc Embossed Mary Janes Size 40 /10 US , NEW! 8B Belle by Sigerson Morrison Black Suede with patent trim Ballet Flats , Ladies Black Leather Clarks Shoes "Discovery Dime"Slip On D Width FittingVia Spiga Perforated Black LoaferAnimal Print black/gray size 41.5Steve Madden Women's Hugh Flat Blue Velvet Size 6.5 eezo , NEW WOMEN'S TEAMCHEER ALLUSION WHITE CHEER SHOES FWCF815 SIZE 8.5Reebok Women's PT Prime Runner Athletic Running Shoes.Pick Your Size. CN2031Nike Lunareclipse 2 + Running Shoes, Stealth/Pink/Volt, Womens 8Womens GUC Silver/Blue ASICS GEL RAVENNA 7 Trail Running Shoes size 9.5 , Puma Sneakers Blue White Women's Running Walking Shoes US Size 6 1/2 , Saucony Womens Redeemer Iso-W Silver/Grey Running Shoes Size 9 (4886) , VANS Fashion Sneakers Gray Textile Women9.5Medium (B, M) , Womens Sz 7.5 Puma Roma Jersey Gray /Orange / White/Shoes , Women's Aldo Flats Economical And Practical Flats , Asics Women's Gel Nimbus 17 US 10 Running Shoe White/Hot Coral/Apple T557N $150New - Drew Paradise II Women’s Black Calf Strap Closure Shoe - Size 8 Wide$159 New Balance Womens 365 Walking WA365BL 7 B M Running Shoes Sneakers , Women's Ryka Sky Bolt - Blue/Yellow/Blue - Width: med - WalkingSkechers Women's EZ Flex 3.0-KINDRED SPIRIT 23475 Lavender Brand New , Nike Air Max Thea TXT Womens Running Training Shoes Size 9 White Gray ,
"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."