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.Sperry Top Sider Cloud Logo Women's Cruiser White/Blue Flat 12M , Bjorndal Womens 9M Brown SOFT Pebbled Leather TRAVELER Comfort Mule Clog ShoesFINN Comfort Brown Suede Mary Jane Shoes - 41 Comfortable Made in Germany , Womens Merrell Shoes Size 10 Lorelei Emme Blue Mary Jane EUC , Women Cute Round Toe Slip On Dress Pump Flat Shoes Casual Solid Ballet Everyday , steno-58 New Flats T-Strap Sandals Gladiator Party Beach Casual Women's ShoesLINDSAY PHILLIPS Liz Ballet Flat - Leopard - MSRP $64! Size 9.5M , Keen Women’s US 6.5 M Brown Suede Leather Fabric Mary Jane Flat ShoesCROCS "KADEE REALTREE" CHOCOLATE/BERRY SHOES WOMEN 8 medium NEW , EUC COLE HAAN Brown Leather Mule Shoe Heel Chunky Clog Slip On US Sz 8 B , Clarks Womens Brown Leather Mules Shoes Size 8BORN Black Nubuck Leather Slip On Size 7 US 38 Euro Clog Mule Shoes W3093 NICE , Shellys Black Leather Emma Platform Oxfords Womens Size US 8.5M , Yosi Samra Women's Samara Sybil Suede Ballet Flats , SAS Mary Janes 9.5 WW Black Snake Print Leather Maria Womens Comfort ShoesNEW BALANCE 860 SZ. 9 White & Blue Sneakers , Nautica Long Bay Slip On Fashion Sneakers 491, White, 7.5 US / 38 EUWomen's Privo by Clarks Black Brown Leather Mary Jane Sneakers Flats Sz 8.5 , Merrell Trail Hiking Shoes Womens 6 Overdrive Brown Chocolate Pearl Blue Walk , New Madden Girl Womens Blush Pink Steep Synthetic Suede Casual Shoes Size 8.5Womens Brooks Ghost 8 Running Cross Training Shoes Size 9.5WOMENS REEBOK CL LEATHER SHMR in colors ALLOY GREY / WHITE / PEWTER SIZE 8Volatile Kicks Size 10 BANGIN Turquoise Leather Sneakers New Womens Shoes , Asics Gel-Nimbus 18 Athletic Shoe - Women's Size 6, Titanium/White/Turquoise , NIKE TAKOS LOW ACG BLACK LIME HIKING TRAIL WOMENS WMNS SZ 6-12 317545-031 , Women's Sperry Top-Sider Boat Shoe CVO Birch Sneakers Size 5.5Sperry Top-Sider Women's Bluefish Boat Shoe, Navy Crosshatch/Linen (5 B(M) US) , SUPERGA Cotu 2210 Classic White Canvas Sneakers Shoe Women's Size 6.5 , Dr. Comfort Sandy Women's Sneakers Size-8M , Women's Teva Hurricane 2 k Sport Sandals Shoes 5 US Dalley Rose New with Tags ,
"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."