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.Womens Size 8M Eastland Brown Leather Slip On Loafers , NWT Anne Klein BK 7M HealsSPERRY ToPSiDeRs Woman Size 6 M Back to SCHooL SHoeS Burlap Neutral , Vintage Jessica Open toed Flat shoes brown, Flower crocheted Look Sz 9MGreat Northwest Clothing Company Womens Black Leather Mule Size: 8Bass Weejuns Katherine III Womens 8 Brown Leather Penny Loafers Slip On ShoesSpring Step Women's Juhi Slip-On Shoe Black , ** FOOT JOY ** White & Brown Great Cond Womens Golf Shoes Soft Spikes Size 5 M$125 NEW JCrew Womens 5 CeCe Suede Ballet Flats Black 46198ECCO Women's Damara Slip On Fashion Leather Sneaker Shoes Green GablesNEW! Skechers Women's GORUN 400 OBSTRUCT Black/Aqua F azRYKA Intent XT womens athletic shoes sneakers White, Light Blue Size 8 Y285NIB Vans Camden Womens Skate Shoes Sneakers 6.5 Cheetah Navy/Coral MSRP$55WOMENS NIKE SHOX TURBO IV + RUNNING SHOES SZ 7 - Pre Owned , NIB Men’s Chaps Genuine Suede Slippers Black Warm In/Outdoor Sz XL 11-12 , Nike Air Vortex Vintage PRM 1st Adoption Sample US 7 WMNS2001 Retro Nike Air Presto Chanjo 105285 441 Women's Shoes XSASICS Womens - Blue Running Shoes Size 9 (291185)Women's Nike Free 5.0 TR FIT 5 running shoes sneakers size 11 , Women's Qupid Women's Tricia-01 Sneaker Various The Kinds And The Styles Athletic Shoes , Women's New Balance, WX40MB,?Cross Trainers, Black/Fin , Salomon XA COMP 7 Women's CS WP Trail Running Shoe 9M , VINTAGE Women's Nike Dunk SB FC Dunk Low Shoes White w/ gold trim worn 2x SZ 9.5CLOSE-OUT! PEARL iZUMi ~ Size 10 ~ Women's Sneakers ROAD N2 Running Purple Pink , SAS Free Time Sneaker - Women's Size 8.5 M, BlackSuperga S00AB60 Women's Fashion Sneakers Black , SKECHERS AIR COOLED MEMORY FOAM FLEX APPEAL 2.0 WOMEN SHOES SIZE 9.5 STNew Womens Skechers GoWalk 4 Fascinate Shoe Style 14914 Burgundy 90W drPuma BASKET ROSE Patent Leather Athletic Sneakers w/Rose Logo White Sz 6-M , Adidas Traxion Women Size US 6 BLACK / PINK FREE SHIPPING BRAND NEW ,
"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."