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.Calvin Klein Pash Flat Square Patent Cap Toe Slip-on Metallic Sheen Size 7 W , Annie White Slip On Casual Loafers Shoes Sz 8 Pleather Silver StuddedBoC BORN Metallic Gray Leather Clogs Slip On Shoes Loafers Wedges Womens 6.5SAN MARINA PARIS Brown Leather Slip On Casual Loafer flowers Italy Size 38, 8usLucky Brand Emmie Red Black Snake Print Ballet Flats Women’s USA 7.5M , Ralph Lauren Blue Leather Women's Loafers Moccasin slip on Shoes Sz 8.5 B , Crocs Womens Isabella Jelly Flat- Pick SZ/Color.Fitflop Due Patent Leather Platform Shoes Black Women Sz 38.5American Rag Stevie Women US 9 Brown Oxford , Dansko Clogs 37 Brown Professional Mandolin Leather Slip On Floral TooledEasy Spirit Devitt Driving Style Loafers, White, 7 USDolce Vita Size 7.5 M Laci Black Patent Leather Ballet Flats New Womens ShoesDolce Vita Black Leather Slip On Cybil Mule Womens Size US 9M MSRP $125 , NEW Rockport M79284 Shore Bets Seaworthy II Loafers, Women's Size 6M, Pewter , Grasshopper Slip On Casual Shoe, White/Cork, Womens US Size 7 , Asics Gel Cumulus 15 IGS Training Running Sz 8Steve Madden Womens Graph White Fashion Sneakers Shoes 9 Medium (B,M) BHFO 9029NIKE PEGASUS 25 SZ 10 M GREEN ATHLETIC WOMEN'S RUNNING SNEAKERSSAUCONY OASIS 2 RUNNING SHOES - MULTI COLOR ( SIZE 7 ) WOMEN'S , New! Skechers Womens Equalizer-Vivid Dream Walking Shoes-Style 12028 73B la , Women's ASCIS Gel Walking Running Cross Training Athletic Shoes-Black-5.5 , Skechers Womens 14232 Black/HotPink Walking Shoes Size 8.5 (352080)Women's Skechers shape ups Fashionable Athletic Shoes , adidas Women's Shoes | Cloudfoam Advantage Sneakers White/Black/White 6 M USNew Womens Skechers Casual Black Work Comfort Slip on Trainer Shoe Size 3-8 UKPearl Izumi Women's EM Road M3 v2 Running Shoes, Deep Wisteria/Algiers , Women's VTG Classic REEBOK Nylon SUEDE Gum Soles ATHLETIC Shoes SNEAKERS Sz 6Propet Womens TravelWalker Sneakers Size 9 Narrow Taupe Shoes , Fila Memory Hxt Sport Athletic Women's ShoesNIKE WOMEN'S GOLD CANVAS AND NEON ORANGE HIDDEN WEDGE PLATFORM SNEAKERS 8.5
"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."