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.Women's Multi Color Warm Winter Knee High Riding Flat Boots Shoes Sz 5-10Chris Craft Womens 6 Shoes Vintage Brown Rubber Boat Shoes Round Toe , Sam & Libby Womens size 6.5 Chelsea Black Bow Leather Ballet Flats Shoes , Womens Grasshopper Green Slip On Shoes Size 9MCrocs Kadee W10 Women's 10 Black Flat Slip on Slingback Ballet Flat Shoes EC , BLACK HOUSE WHITE MARKET Women US6.5M Black Leather Barcelona Flat Faux FurWomens minnetonka moccasins size 7 NEWSteven By Steve Madden Hilda Casual Shoes - Women's Size 8.5 M, BlackClarks Original Wallabee Women's 8.5 M Brown Oiled Leather Comfort Casual Shoes , NEW SKECHERS RED SLIP ON WALKING COMFORT WEDGE SIZE 8.5 M $65 , White Mountain Womens ALFRESCO Fabric Closed Toe, OffWhite/Black, Size 7.5zapatos mujer Spring Women Flat Platform Loafers Shoes Ladies Suede Leather sexy , Seychelles Women's So Nice Fashion Sneaker , Bobs From Skechers Women's Triple Decker Black Casual Shoe 6 Women Us , ASICS Dynamic Duomax Athletic Running Sneakers Silver Pink Women's Shoes Size 8M , Bolt women's shoes 8 1/2 purple zipper soft , Ladies Shoes Cherry Mikee Black Navy or White Leather Slip on Wedge Shoe 5-10 , New! New Balance Womens 750V2 Running Shoes-Style W750BG2 171F ilSimpsons Homer Velour Mule Slippers Novelty Mens Slip On Warm Fun Navy Character , PUMA Womens - White Fashion Shoes Size 6.5 (413121)VANS. Women's or Men's CAMRYN SLIM Casual Canvas HI Shoes. Wom. US 10, 10.5 & 11*Converse Baby Blue Converse Size 7 , Nike Air Force 1 Women's 07 “RED LIZARD” Shoes Beet Swan 315115-615 Size 9 RARE , Men's Shoes Slippers Glerups Boot Slipper Brown 43.0 Fast Shipping Slippers , LOWA TEMPEST BROWN LEATHER SNEAKERS HIKING TRAIL WALKING SHOES BOOTS WOMENS SZ 7 , Nike Youth SB Stefan Janoski Premium Canvas Shoes 654862 101 Sizes: 4.5 ~ 7 , Adidas Galaxy 4 Running Shoes (B43837) Women Training Sneakers TrainersTeva Womens Hurricane Volt Sandal ShoesVintage L.A. Gear Womens Sneakers Size 7.5 Brown Shoes Retro 80s 90s AthleticSkechers Sport 61/2 Black Relaxation Fashion Comfort Sneaker Memory Foam 22463
"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."