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.Women's BORN BOC 7.5M BC3129 Black Leather Wedge Clogs/Mules Slip On Shoes , New! Women's Bongo Yogi Espadrille Flat Casual Shoe Choice of two colors 302B lr , Down To Earth Black Flat Leather Shoes F8993 (R1A) , Women's NATURALIZER Coral Pink Flower Travel Ballet Flats Slip On Shoes Sz 6.5 MINDIGO BY CLARKS MAGENTA REPTILE PRINT SLIP ON WOMEN SIZE 5.5Bernie Mev Black Black Flats Size 37 NEW , SAS Women’s Walk Easy Be Happy Shoes Sz. 6 Black Leather, USAWomens 9 Steve Madden Pembrook Leather Oxford Heel Formal Casual Shoes - BrownIsaac Mizrahi Billee Blue Suede Bow Driving Moccasin 6.5 New , Sperry Top-Sider Angelfish Navy/Fish Stripe Boat Shoes STS93261 NIB Sz 8.5 MClarks Medora Jem Casual Slip On Shoes - Women's Size 7 M, Navy , Banana Republic Pointed Toe Robin Ballet Flat,Midnight gingham SZ 6.5 v , Aerosoles Womens Good Times Leather Closed Toe Loafers Black Suede Size 7.5 , Saucony Ride 5 running shoes white blue & yellow womens 7.5 seven 1/2 38.5 Euro , Steve Madden Womens Graph White Fashion Sneakers Shoes 9 Medium (B,M) BHFO 9029 , ANTHROPOLOGIE FARYLROBIN ELLISON SHEARLING LOAFER sz 7 (AS IS) , BCBGeneration Womens Gray/Black Metallic Leather Shoes 6 M , Cole Haan Resort Italy Loafer Moc Toe US 8.5 C Women Red Leather , NEW Skechers EZ Flex Memory Foam Womens Slip-On Walking Shoes 7W Multi MSRP$60 , Sam Edelman Womens Baylee Blush/Dusty Rose Fashion Sneaker Size 8 (24913)Reebok Prelaris 972 Womens 6M Max Trax slip resistant shoe Black , Women's Via spiga 8.5 new New Products FlatsWomen's rasolli shoes Clients First Flats , New Balance Women's WMD500V3 Middle Distance Spike Shoe , Nike Women’s Purple/Gray Size 6 Pre Montreal Racer Sneakers RN , Original Kitson Smile 34521 BKPK Casual Women Shoes , EUC J Crew New Balance 696 Womens $85 Sneakers 9.5 M Classics , New Gola Panas Womens Slip On Trainers ALL SIZES AND COLOURSNew 12404 Skechers Sport Women's Heart To Heart Fashion Sneaker, Navy/Hot Pink , La Sportiva Ultra Raptor GTX Trail Running Shoes Women Size 9.5 ,
"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."