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.Mark Lemp Classics Becky Women's Flat 10W , Bare Traps Brown Fabric Man Made Slip On Slides Shoes Women's Size 7 , SAS Tripad Comfort Loafers 8M BrownSloggers Women's Blue Slide On Shoe Moisturizing Wicking Thermal Insole Sz 9 ✞ , Ecco Women's Brown With Pink Suede Leather Loafers Flat Shoes Size 40/9 - 9.5 , NEW!! Catherine Malandrino Forrow Red Velvet Slides Mules Size 8.5M US 38.5M EUBass Womens Porto Leather Casual Comfortable Walking Shoes Black Size 6.5 W , Easy Street Sport Laurel Slip On Shoes, Women's Size 7.5M, Brown NEW , **Sam Edelman Danica Mules, Women's Size 9.5 M, Gold/Blue , Sperry Top-Sider Pennyfish Linen Sparkle Leopard Boat Shoes Womens Sz 8 NIBWomens Air Max 2011 Running Shoes Size 6.5 , Women's Puma Shoe's Size 9.5. ccRYKA "FREELANCE" LEATHER WALKING SHOES LADIES US 7.5 med NEWWomens Casual Sports Flats Loafers Shoes Slip On Mule Sneakers Plimsolls CanvasSteve Madden Womens Graph Black Fashion Sneakers Shoes 8 Medium (B,M) BHFO 2497 , U.S. Polo Assn. Candice9 Sneaker - Women's Size 7.5, Black , $110 ADIDAS VISTA CLIMAPROOF GREY/BLACK HIKING SHOES US 9M , Brooks Running Shoe Caldera Women's Anthracite/Azalea/Black 11MClarks Dowling Pearl Walking Shoes 537, Black Synthetic, 8.5 US / 39.5 EU , Nike? ~ TRAINING Run Shoes ~ Everyday 917707-400 ~ Women Sz 9 ~ GOOD , Adidas ADI Ballerina W Men's Shoes Size 7 , Skechers 14118 Womens GOrun 5 Running Shoe- Choose SZ/Color.Ladies Clarks Active/Outdoor Trainers Outlay South , New Under Armour Women's Micro G Assert 7 Running Shoes Size 7 - Graphite / BlueSaucony Women's Kinvara 8, Berry/Pink, 11 M USWMNS air force 1 hi Suede , Womens Polo Ralph Lauren Corduroy Shoes Red Brown Sz 7.5 or 8 or 8.57/37.5 REEBOK Womens Running Walking Shoes Sneakers Blue/Gray/White , Nike Blazer mid suede vintage womens trainers sneakers shoe 518171 611 NEW+BOXVans AUTHENTIC Hemp Linen Turtledove/White Women's 5.5 ,
"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."