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.Brighton Franki Brown Leather Slip On Mules Comfort Shoes Women's Size 7.5 EUC , TS shoes TAKING SHAPE sz 6 / 37 Anastasia Black Leather Sandals flats slides NIB , MERRELL " Plaza Bandeau" Womans size 6.5 slip on shoes- SALEAEROLOGY Loafer/Shoes~Womens Size US 8~Black~Buckle Detail~EUCNew womens canvas shoes size 7 , Clarks Womens Loafer Shoe Size 7.5 M Brown Leather Slip On “violet” FlatsJessica Simpson Women's Mandayss Ballet Flat , Klogs Spokan Womens Polyurethane Clog Display Model Shoes Chestnut 14 M , EARTH SHOE ~INVOKE~ SANDSTONE Brown LEATHER SLIP ON OXFORDS W'S 10 BFerragamo Calf Leather Tan Pebble Stitched Penny Loafers Italian 7.5 AA Narrow NMERRELL SKYNIGHT SLIP ON CASUAL Women's LOAFERS Shoes Size 10 EUCFranco Sarto Women's Shimmy Black Ballet Flat Size 7.5Klogs Odessa Women's Display Model Shoes Mustang Copper 7 M , Stuart Weitzman Black Round Toe Pump 2.5" Chunky/Block Heel SZ-7N vtg $185 Ret , Anne Klein Valarie Wedge Shoes - Women's Size 8M - BlackNaturalizer Womens Saban Solid Round Toe Casual Loafers Shoes BHFO 1181 , Sperry Top-Sider Women's Seamate Black Fashion Sneaker 10MOlukai Womens Nohea Perf Suede Leather Slip On Loafers Comfort Shoes 6.5NEW F Troupe White Leather Buckle Saddle Shoe Loafer Bathing Shoe Women's 6Danskin Womens Athletic Sneakers Running Walking Gym Shoes Neon Pink Yellow 6 , Women's totes Women's Ruby Black ngenious And Practical Athletic ShoesWomen's Zara sneaker in white Finely Processed Athletic ShoesASICS Women's Gel-Rocket 8 Volleyball ShoePleaser Pink Label Women's Kimberly 04 Wedge Sandal Red Patent Heeled SandalsNew! Saucony Women's Fastwitch 6 Road Running Shoes in Purple Size: 8 in box$110 The North Face Ultra Guide Women's Shoes Sneakers Size 7 , New Balance Women's WW669GR Comfort Athletic Trail Walking Shoes GrayNike Women's Air Relentless 6 Running Shoes Women's Size 10 , NEW COLE HAAN WOMENS WOMEN'S PINCH WEEKENDER LX LOAFER - GOLD SOKO WASH-GOLD-... , NEW BALANCE 410v5 Trail Running Shoes Womens Sz 8.5 wt410cx5
"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."