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.Jonas rules tennis shoes sz 13 by Disney , Dansko 4401242400 Suede Women's Shoes SZ 7.5NEW Butterfly Twist Gigi Rose Gold Metallic Espadrilles Foldable Shoes Sz 5M , Nice Black Leather MINNETONKA Slide Clogs Sz 8Unisex Adults Birkenstock Madrid Nubuck Beach Holiday Open Toe Sandals All Sizes , NEW SAS Tripad Comfort EASIER Womens 9 M Gray Metallic Leather Loafers $140 , Eric Michael Womens Shoes NEW $145 Omar Black Taupe Suede Slip On Platform 35 5 , Brand New GUESS WGKRYSTA-R Hi Tops Fashion Sneakers Shoes Denim/ Silver Size 6.5 , Women's Athletic Running Shock Sneakers Outdoor Casual Breathable Sports ShoesWomens Running Trainers Walking Shock Absorbing Shoes Sports Fitness ShoesChic Women Rivet Squart Toe Low Block Heel Slip on Pumps Oxford Loafer Shoe Y835 , Aerosoles Women's Exhibet Ballet Flat - Choose SZ/ColorCOLE HAAN AIR KAYDEN OXFORD SHOES WOMEN'S 10.5 B NIB , GH Bass Anchor Gold Shimmer Women's Boat Deck Shoes size 11 Leather NEW!reebok suede sneakers shoes size 5 , size 8 women's Nike training shoes running walking , Women's "LA GEAR" Beige Suede Leather Athletic/Running Shoes Size 4CONVERSE All Star Low Top Pink Canvas Shoes Womens Size 7 FAST SHIP! , Bearpaw Emma Short Women Black Suede Leather Slip On Sheekskin Winter BootReebok Realflex Fusion Tr U-Form+ Shoes Sneaker Trainer Sports Shoes , NEW! Ellen Degeneres ED Farley Grey Suede Slip On Sneaker Women's Size: 7.5 , Diesel Vtg Savah Red Cream Leather Walking Sneakers Tennis Shoes Womens Size 6.5Womens Nike City Loop Huarache Style Running Shoes Blue/Black/Grey AA1097-400Reebok Classic Leather Shimmer Womens Light Pink Suede Trainers , SPRING COURT Women's G22 Cold Dye Fuchsia/White Canvas Sneakers Shoes US 10 / 41 , Saucony Women's Zealot Iso 2 Running Shoes Teal/Citron Sizes 6.5-11 (B, M) , Nike WMNS Woodside II Hi Cool Grey Bordeaux lot 537347 006 Size 9.5 , Brand NEW New Balance 710 Sneakers, Running Shoes, size 9.5, never been worn! , New in Box Women's size 9.5 Greenjoys Footjoy Golf Saddle Shoes, BlackNew Balance Women's 928v2 Walking Shoe Black Size 10.5B WW928BK2 New In Box ,
"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."