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.02-1955 Women's Drew Delite Mary Jane, Adult Women's, Size:6.5WWBella Vita Tavie Women's Camel Flat 8.5XW , Purple Jelly Soft sole Slip-on Only Round Toe Womens Ballet Flats Shoes Size 9 , COLE HAAN black suede loafers logo tag shoes 6 aa Vibram soles EUC , Clarks Bendables Loafer Dark Brown Leather Casual Zip Zipper Shoes Womens 7.5 M , Ladies Spot On Wedge Heel Shoes F9722 , TALBOTS Women's Pink Patent Leather Open Toe Flat Shoes Size 6 1/2 B , Women's Skechers 49258 Navy Blue Slip-on Casual Moccasins Size 6 MKhombu Tan Casual MaryJane Cross Strap Walking/Water Shoes Women’s Size US 7.5MRialto Sunnyside Ballet Flats Shoes Bow Size 9M Metallic Silver Black Comfort , Mephisto Black Embosses Leather Square Toe Driver Loafers Size 8GUJA Milano Women Slip On Moc-Toe Penny Loafers Size 6.5 Black Leather , Skechers Womens Bobs B-Loved Round Toe Loafers Black Size 8.0 u2SH , Jeffrey Campbell Play Canvas Platform Shoes Womens Khaki High Top TrainersReebok Sublite Women's Shoes Sz 10 Black /Gray/Pink Memory Foam Soles! ??SKECHERS SHAPE UPS 11809 Womens Navy Blue White Walking Toning Sneaker Shoe 9.5M , Women's Skechers Go Flex 2 - Charcoal - Width: med - Walking Size 9 = , NEW OLD STOCK Vintage Candies Retro Canvas Tennis Shoes Size 7 in box HIPSTERPropet Women's Dayna Ankle Bootie, Dark Red, 7 2E USSkechers Women's YOU Slip-On Sneaker White/Black Walking ShoesMerrell Around Town Sunvue Slide Women's Size 7 Black Texture 25%OFFNew Balance Women's Wzantbx3 Black Size 5.5Vans SK8 HI SLIM ZIP Leather Wind Chime/Blanc De Blanc Men's 10 Women's 11.5adidas Gazelle - Green - Womens , NIKE AIR ZOOM ELITE 8 SIZE 7-7.5 WOMEN'S RUNNING SHOES (748589 003) , Asics T4K8N GT-1000 3 Duomax Neon Running Training Sneakers Women's US 7 , Vans Sk8 Hi Del Paro MTE All Black Women's 8 Skate Shoes All Weather NewREEBOK WOMENS CLASSIC LEATHER DIAMOND BD5757 Diamond-Silver Met/Grey/WhiteK-Swiss 95577-102-M Womens Gen-K Icon Sneaker- Choose SZ/Color. , RYKA Ryka Womens Hydrosphere Cross Trainer- 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."