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 SAS Tripad Comfort Loafers Shoes Brown Size 9 Nearly New , Stuart Weitzman Womens 7 M Blue Crocodile Leather Buckle FlatsNaturalizer Womens Size 7.5 Medium February" Brown Suede Slip On Comfort Shoe , Voda Women's Klassy Slip-On Flats - Pink - Size 8Women's 8 M Simple Black Polkadot Cream Flats A073 , Marc Joseph Women’s 8 Loafers Leather White Grand Street Hardware Driving ShoeClarks Womens Size 8.5 Black Loafers Bendables Ashland Alpine Leather Shoes , INDIGO by Clarks Womens 6M Flower Applique Suede Slip on Mules Clogs Tan P05Black Slip On ComfortABLE Flat Shoes Sz 8W NWOT , London Sole Ballet Flat Brown Suede Size 38 , DVF Leopard Print Calf Hair Ballet Flats (SIZE 36)Women's Shoes Clarks Sillian Stork Casual Cushioned Slip Ons 25893 Navy *New*Women's Aerosoles, Medieval Slip-on Brown Loafer Size - 11 US / , BC Footwear Women's Happy As a Clam, Orange, Size 9.0Adidas flats black white fringe ankle sport shoes 7 37.5 4.5 , Nike Women's Pink White Mint Ballerina Flat Summer Cotton Casual ShoesPUMA Womens Asha Alt 2 Gray Slip On Casual Sport Athletic Shoes Size 8 IP-401 , Deer Stags Nordic Moccasin Slipper Shoes, Men's - Size 11 M, BlackNEW NIKE Zoom Rival XC Track Shoes WOMENS 10 Black Lava Green 749351-083 $65 , EUC Skechers Shape-up Women's Shoes Size 8 Color Black, White And GrayWomen's Salvatore Ferragamo New Varieties Are Introduced One After Another Flats , Ladies Clarks Trainers Label Outlay SouthAerosoles SIDE TRACK Womens Side Track Fashion Sneaker- Choose SZ/Color. , ADIDAS ENERGY BOOST 2 ATR Running Shoes WOMENS SZ 7 Core Black/White TechfitSaucony Women's DXN Trainer Fashion Sneaker - Choose SZ/Color , Skechers Performance Women's Go Walk Black Slip-On Walking Shoe Sizes!! NIB New , Newton Terra Momentum Trail Shoes Womens Size 10.5 (never worn)Geox Fashion Sneakers size 7 M Glitter Sparkle Shoes New WF34Used SKETCHERS Shape Ups Women's 7.5 Shoes Sneaker White Silver 11814 , New Balance Womens WLD5KV4 Track Shoes- Pick SZ/Color.
"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."