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.NATURALIZER~Brown SUEDE LEATHER UPPER Casual FLAT SHOES~Women's 7.5N , gloria-33 New Fashion Nubuck Slip On Casual Women Flats Women Shoes Red 8.5 , Ladies Rockport Adiprene Burgundy Leather Slip On Shoes SK59715Women's Summer Fashion Slingback Buckle Cork Wedge Sandal Shoes All Size 5 - 10 , CLARKS Clogs Wedges Sandals SWEET GEORGIA Open Toe Womens Shoes Leather Sz 7.5ECCO Womens Sz 40 Oxfords Fashion Sneakers Casual Shoes Beige Leather (A3)JOSEF SEIBEL CORA Mary Jane Brown Green Leather Shoes Sz 37 (BG14) , BCBG Max Azr Stella 7.5M Pony Hair Patent Loafers Flat Shoes Leopard Print NEW , Comfort by Rockport Casual Shoes Womens 8 Grey Gray , Ladies Cole Haan Black tasseled loafer size 9 A ACole Haan Rodeo Tassel Loafers 042, Light Blue, 6 USJournee Collection Womens elina Closed Toe Ankle Strap Mules Blue Size 6.0Skechers Womens Bobs B-Loved Round Toe Loafers Black Size 6.5 ioH3Ladies Down To Earth Leather Slip On Shoes UK Sizes 3-8 F80204 , TRASK Pamela Perf Mule W's 6.5 , Nine West Shoes Heels Slingbacks Textured Heel Peep Toe Black Womens Size 7.5 M , New Womens Skechers Omne Kort Klassix Shoes Style 720 Black 70E dr22683 Skechers Womens EZ Flex 2 A-Game Memory Foam Casual Grey/Coral , Women Merrell Shoes flat Sedona Brown Hiking size 8 Karhu air cushion TorsionPUMA Voltaic 5 Running Shoes, Wht/Purple/Lavender,Womens US 9.5 , 02-1520 Tommy Hilfiger Women's Jolli SIZE 11MKeds Womens Chillax Low Top Slip On Fashion Sneakers Pink Size 6.0 nOsXWomen's propet womens shoes size 9 Bargain Price Athletic Shoes , Women's Puma Star Be Novel In Design FlatsSkechers Women GO WALK Recovery 13514/GYTQ Gray/Turquoise Walking Shoes , Women's Nike Free TR 5 Flyknit Training Shoes NEW Turquoise / Energy , MSRP $120 , New Balance Womens - White Walking Shoes Size 5 (339975)Converse 537080F Womens Chuck Taylor Shoreline Slip Casual Shoe, Navy, Size 5.5 , Brooks GTS 16 Womens Size 8 Teal Silver Athletic Running Shoes DNA , Salomon XA Pro Women's Pearl Grey/Bordeaux/Hot Pink Running Shoe 6M
"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."