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.Ecco Black Zip Closure Leather Slip On Comfort Loafers Shoes 6.5Womens 6M PRIVO by Clarks Black Leather and Suede Casual Driving MaryJane FlatsSanita Professional Clog Women size 41/10-10.5 Black Leather , WALKING CRADLES FAWN MICRO BLACK SUEDE Walking shoes 10 NEW IN BOX , HUSH PUPPIES H500438 WOMEN'S VERSE BLACK LEATHER CASUAL SHOES NEW IN BOX , Steve Madden Women's Black - Slip-on Sneakers - Whilma - SIZE 9G.H. Bass & Co. Marina 2 Women's Camouflage Moccasin Boat Shoes Loafers US 8 MWomen's SAS METRO Brown Nubuck Leather Loafers w/ Bit Sz 10 NarrowTOPSHOP KISS GHILLIE tassel gladiator ankle wrap pointy toe suede flats shoes 6DEXTER White Kilt Women's Golf Shoes Sz. 6-1/2 MClarks Propose Spire Loafers Flats Brown Shoes Vegan Womens Size 6 MBernie Mev VERONAWEB-WHITE: Womens Verona Web White Loafer , Brooks Trance 10 Sz 7.5 Women Silver Lavender Running ShoesKeds Women Size 8.5 Slip On Casual Sneakers EUC WF22423MBillabong Women's Phoenix Fashion Sneaker, Black/White, Size 6.0 55JRNew Balance 609 Walking Shoes, Women's Size 10 B, White , Clarks Brown Snake Leather Azella Major Slip on Espadrille Sneakers 6 SALE , Adidas Womens SpringBlade Running Shoes G66650 Shoes Sz 8 EUCWomen's KEEN VERSAVENT WOMEN Modern Design Athletic Shoes , Women's enchanted Shoes 380307 Gold 36 Surprise Flats , $240 SCHUTZ AILA Gold Double Buckle Crinkle Leather Designer Sneakers 10 , Columbia Whitney Ridge Womens BL3805-051 Shale Grey Hiking Trail Shoes Size 9.5New! Saucony Womens Powergrid Triumph 9 Running Shoes-10137-1-Sz 6 NIB la- W125BOUTIQUE 9 MIRABELLE Natural Patent Designer Pumps Heels 8.0 M , NIKE W TENNIS CLASSIC ULTRA FLYKNIT 833860-301 OLIVE FLAK ROYAL BLUE SIZE: 6Vintage 1980’s Reebok Boston Road Women’s Running Shoes – Size 7 – White , Fashion Womens Wedge Heel Sport Shoes Athletic Cozy Ankle Boots Warm Casual Chic , ax26 CIABOO shoes red canvas women sneakers , New Balance Women's 696 Sport Shoes Red , Nike Shox Women's Running Training Shoes Size 10 ,
"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."