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.Pre-owned SAS Black LEATHER Mock Toe WEDGE HEEL OXFORD SHOES WOMENS SZ 5.5M USA , Women's Clarks Black Leather Mules, size 8.5 , Earth Shoes Ladies Size 5.5 Brown Leather Slip On Loafers Flats , Lucky Brand Women's Carlyn Ballet Flat , KEEN 59010 US 7M Smooth Black Leather Slip On Ballet Flats Shoes w Cush , MERRELL MOC PRIMO SEAM BLACK SUEDE LEATHER MULES SLIDES CLOGS SHOES - SIZE 7SAS Womens Work Shoes Loafers Black Patent Leather Croc Embossed Size 9.5NTommy Bahama Size 9.5 Tan Suede Loafers New Womens Shoes , Espace Size 6 YOKO Black Fabric Slip On Flats New Womens ShoesSteve Madden Womens Kerry-L Slip On Loafer Shoes , SUPERGA 2210 COTW Women Slip-on (8.5 M, NAVY) , Sperry Bahama Canvas Boat Shoes, Women's Size 11M, IvoryWOMENS BROOKS RAVENNA 6 RUNNING CROSSFIT ATHLETIC SHOES - SIZE 8.5New!! Womens Skechers Synergy SN 12098 Sneaker/Cross Trainng Grey/Blue [141D] , NEW Speedo Women's Port Shoe Lightweight Breathable Water GRAY Boat Shoe 9 , Gola Women`s Hi-Top shoes New Sz 6 U.S. ''Corduroy'' , TIE DYE SLIP ON WOMEN ALEX-3-18 BLACKSWAN GREENNEW Rachel roy Isabel Suede Ballet Flats Black Size 7Lucky Brand Womens EMMIE Leather Closed Toe Ballet Flats, Black, Size 9.0 27s5Womens ASICS T6A9N GT-1000 Running Shoes Black on Black Size-8 D , Naturalizer Womens Carly Blue Fashion Sneaker Size 8.5 (29135) , New Women's Skechers Flex Appeal 2.0 New Image Slip On Shoes 12752 Black dc 9CMe Too Stretch Slip-on Loafers - Baylee navy 5-1/2 medium , New Nike Women's Zoom Rival Waffle Grape or Jade Size 7-11 $60ASICS Gel Fluent White Pink Silver Trail Running Shoes Women Size 8.5 A1202 , Women's DRAVEN Slip ons Easy-to-clean Surface Flats , Skechers Performance Women's Go 4 Walking Shoe,Burgundy,8 M USMint Condition NIKE Free TR Flyknit 5.0 718785-402 Womens 9.5 41 EUR , Womens Merrell All Out Blaze Sieve MJ Sandel Sneaker Shoes Sz 11 , Womens REEBOK CL NYLON PJ Stucco Trainers BS7607
"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."