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.Born Wool Clogs Women's US 10 Woven Shoes Tapestry Mexico 2 In Heel , WOMEN FLAT FRINGE BROUGE LOAFER WORK EVERYDAY SHOES IN BLACK FROM SIZE 3 , Minnetonka Moccasins Fringe Shoes Size 7 1/2 Suede Tan Womens , Mossimo Size 8 Purple Velvet Flat , Women's Size 8 1/2 Medium L.L. LL Bean Brown Clog Slip Ons Shoes Canvas Closed , NWT Sam & Libby GUNMETAL Gray Silver Metallic BOW Flats Shoes Womens 6.5 M , Fantastic 9 West Kingbird Size 9 M Weave Leather Upper Flats Shoes , Amalfi Black Leather Peep Toe Flats US 10 Womens Exclusively for Nordstrom Shoe , ** Rialto Sofie Flat - Women's Size 6.5M Black , Ash Black Embossed Sneakers Size 10Roper Performance Women’s Tan Suede Slip Ons Shoes Size 7 S1Nine West Womens Onlee Pointed Toe Slide Flats, Light Natural, Size 7.5 , New Womens 10 M MINNETONKA MOCCASINS Fringe Shoes Genuine Suede COGNAC USA , Cole Haan City Women's Black Leather Loafers Size 6.5 B Slip On Italy ClassicAddidas Women's Athletic Shoes - sz 9.5 Worn a few times, Clean / Nice , Women's Cow Leather Flats Slip On Oxfords Comfort Ballets Loafer Driving Shoes , SPRING STEP WOMEN'S COMFOR ATHLETIC SHOES SIZE 42 US 11ASICS Gel Equation Running Training Shoes Womens Ice Blue Hot Pink 9.5 T3F6N , Baffin Cush Booty - Grey - Mens , Skechers Women's Sz 7 Gray & Black Leather Textile Active Walking Shoes SneakersNike Free 4.0 V4 Running Shoes, White/Grey/Mint, Womens US 6.5MBT Physiological Footwear Sneaker Chapa W White Swiss Engineered US 8Women's Brooks Pure Flow 6 Aesthetic Appearance Athletic ShoesAsics GT2000 FluidRide Dynamic Duomax Sz 8.5/40 Ret$ 140 , Nike Wmns Air Zoom Fearless Flyknit Black Green Women Training Shoes 850426-002 , Aerosoles SIDE TRACK Womens Side Track Fashion Sneaker- Choose SZ/Color. , Asics Women's Gel-Fit Tempo 3 Ankle-High Running Shoe , Nike Air Max Team ST Running Training White & Green Sneakers Shoes Womens 6.5Aerosoles Womens Fundraiser Sneaker- Pick SZ/Color.REGATTA athletic trail shoes GREAT OUTDOORS X-Ert waterproof hiking UK rare ,
"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."