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.NEW WOMENS 9 TWISTED SHOES SLIP ON FREE SHIPSperry Topsider Grey Leopard Print Boat Shoe , SAS Women's Slip On Penny Loafer Comfort Shoes Size 7.5 N Tripad Comfort Beige , Ladies Sandpiper Casual Loafer Shoes EvaLADIES DOWN TO EARTH ORANGE LEATHER CASUAL SHOE STYLE - F3096 , Dr Scholls Women Loafers Size 8 Medium Tan Nude Style 69831 , Franco Sarto Womens Porter Leather Closed Toe Mules Cocco Le Size 9.0 L2aMTalbots Women's Suede Ballet Flats Size 6B USMerrell Womens Slip On Shoe US 7 Encore Adams Dark Earth Suede Leather Eur 37.5 , Minnetonka Moccasin Women's Dark Navy Cally Trapper Moccasins Sizes: 6,7,8,9 &10J-41 By JAMBU MARTINI Vegan Tobacco Brown Mary Jane Flats Shoes Women's 11 MSam Edelman Fallon Flats - Women's Size 7.5 M, Light Pink , Ballerines Babies à Talons Cachés en Cuir Marron et Kaki PALLADIUM T 39 TBE , B35 Hint Slip-On Sneakers 654, White, 7.5 USNike Air Torch 4 Womens Size 10 Black Running Shoes Sneakers Pink SwooshNew Zara Leather Sling Black Heel Brown Block Mule Round Toe Sz 5 SpainPropet Caylee Slip On Shoe - Women's Size 6.5M, BlackNWT WOMEN'S VANS WM ATWOOD LOW (CANVAS) SNEAKERS/SHOES.SIZE 7.NEW FOR 2018! , Black Diamond Women's Momentum Climbing Shoes (Aluminum) Size 9.5 US , MERRELL Proterra Vim Athletic Hike Walking SEA SHORE Women Shoes Sz 7.5 / 38 EU , Women's Modern Fiction Ballerina Crazy Price, Birmingham FlatsAsics Women Gel-Saga (gray / soft gray) H484N-1010 , $170 Vivobarefoot Womens Hybrid Golf Shoes, White, / US 6Lucky Brand Women's Brenny Ghillie Strappy Sandal Cafe Leather Strappy SandalsZee Alexis Womens Kerrigan High Top Sneakers Olive 7.5 MSeven Dials Women's Andele Platform Sneaker Black Satin Fabric Sneakers , SALE @ NIKE FREE 5.0 Limited Leopard Cheetah 511281 Sneaker Shoe Women Sz 8 ??b1 , Women's Under Armour 1295755 002Speedform Sling Wrap Shoe 7New Nike Womens Free Rn Cmtr Run Commuter 2017 880842-301 sz 10.5 sequoia greenNike Flex Fury 2 Lightweight Running Shoes, Women's - Size 9.5, Black ,
"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."