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.A2 by Aerosoles, Women's Size 9-1/2 M, Rock Solid/Tribal Fabric, Flat Shoes, NIB , Lucky Brand Womens Emmie Blue Ballet Flats Shoes 8.5 Medium (B,M) BHFO 9287B.O.C. BORN Brown Leather Woven Braided Band Slide Mules Clogs Size 9Merona Women's Brown Textile Slip On Pointed Toe Ballet Flats US Size 8$130 size 7 Ivanka Trump Lama Pewter Leather Flat Loafers Womens Shoes , US PUNJABI JUTTI FLIP FLOP KHUSSA SHOES INDIAN SHOES MOJARI WEDDING SHOES DD973NATURALIZER Women's Black Strap Patent Upper Shoes Size 7.5 W Wide , DR MARTENS Cut-out 3-Eye Leather Shoes / / US 7 RRP $249 *SMALL MARKSALEGRIA Womens sz 38 Mary Janes Shoes Fel-709 Metallic Snake Print US 8/8.5Easy Spirit Lt Blue Stripe Travelport Sneaker Slip on Mule Clogs 10 New , Hotter Women's Sunset Shoes Black GG8 Size UK:8 US:10M $95Columbia Dakota Drifter Waterproof Hiking Shoes, Women's Size 7, PebbleMerrell J178605C Women's Performance Walking Pull-on Shoes Black size 7 M , Skechers Womens Black Suede Leather Sporty Fashion Sneakers Shoes Size 6Tamarac by Slippers International Mens Cody Sheepskin Slipper,Rootbeer,12 M USNew Steve Madden Mens Pfire Cognac Mule Slippers Size 8 (33234) , Women's Under Armour 1296214410 Street Precision Slip Ons Midnight NavyMerrell M-connect series women running shoe size 7 Plum color NEW , Cole Haan Women's, GrandPro Tennis Sneaker, Optic White/White, Sized 9.5BVintage 1980's Rare New Balance Rainier Low Cut Hiking Shoes USA Women's 7.5 B , Women's Cole Haan Women's Paz Sandals The Queen Of Quality FlatsWomens Nike Flex Contact Size 8.5 Black White 908995 002 , Brooks Glycerin 15 Blue/Purple Running Shoes Women's US Size 6 (F1,1) , Brand New Nike Air Max Thea SE Metallic Hematite Women Sz 8.5 861684 002Converse All Star Women's Teal Shoreline Sneakers F Size 5 US TealNEW-Women'S Skyscape Runaround Zebra Print Walking Sneakers White/Grey-SIZE 6MNIKE AIR womens silver gray pink athletic shoes sneakers size 9New Womens Skechers Gratis Leacey Shoes Style 22764 Black/White 91V hrNIKE Women's Revolution 4 Running Shoe Platinum/Sunset Pulse-Wolf Grey, 7 US 2E , VASQUE -GORE TEX/Genuine Leather Hiking Boots-Size 8W Wide-Beige--Nice condition ,
"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."