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.Shoedazzle Carolyn Black Multi Woven Patent and ManMade Dress Flats-6.5M , Women's Bandolino Alist Black/Beige Flats Size 7 M NEWCole Haan Turquoise Leather Gold Accent Heel Ballet Flats. Size 6.5 B.Franco Sarto Womens scranton Leather Pointed Toe Mules, peach su, Size 6.0 qbY6Traditional Handmade Women Shoes Leather Flip-Flop Ballerinas Mojari US 6.5/7.5Strictly Comfort Womens 8M Mule Slide Brown Penny LoaferGabor Metallic Perforated Leather Rounded Flats Black Size 8.5 USLPB Ballerine Noeud Ella F Noir , Womens Havaianas Slim Logo Metallic Holiday Lightweight Rubber Flip Flop US 6-11Isle Jacobsen Tulip 139 Black Slip on Women’s Shoes, Size 40 NibAriat Sport Barn Paddock Clogs Leather Size 7.5BEUC Sesto Meucci Ballerinas Flats Leather Patent Captoe Tweed Fabric Sz 11 ItalyLL Bean Women’s Dark Mocha Brown 8.5 Mocs Insulated! School Special! , Rose Petals by Walking Cradles Eagle Moccasins Tobacco Napp Size 5 M,NEWBZees Women's Cruise Slip-on, Navy, Size 8.0 , Dansko Womens Shoe Size 39/9US Burgundy Leather Button Mary Janes BB18New Foot Petals Womens Blair Gold/Multi Fashion Shoes Size 6.5Chic Women Spring Breathable Wedge Heels Sneaker Breathable Loafers Shoe Slip OnWomen's Simple Burgundy Leather Fashion Sneakers US 8Women's Nike Zoom Courtlite 3 Platinum White Black Blue Tennis 487996-001 sz 9.5Skechers Flex Appeal 2.0 Athletic Women's Shoes Size 9.5 , Women's vans old skool white leather Online Athletic ShoesWomen's L space Flats Fashionable FlatsNike Women's Roshe One Winter Running Shoes Black/Black-Sail 685286-001 Sz 7.5NEW Reebok Royal Transport M48504 Womens Shoes Trainers Sneakers SALE , ASICS Womens - Blue Running Shoes Size 9 (347104)Women's Nike Juvenate Womens Size 10 White Running Shoes 724979-103Asics Kayano 23 Black Women Size 7.5 , Skechers Shape Ups X Wear Hyper Active 8.5 Black Mary Jane Walking Toning Shoes , Womens Nike Free RN Motion FK 2017 Size 8.5 (880846 004) No Box
"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."