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.$69 size 7.5 Bare Traps Mitsy Black Memory Foam Flats Slip On Womens Shoes , French Connection Womens Maci Red Oxfords Shoes 7.5 Medium (B,M) BHFO 0533PLEASER Silver Metallic Ballet Flats Women's Shoes Large SIZES ANNA01/SPU , Vera Wang Womens Green Suede Flats Shoe Size 5.5 M , NEW Rockport V77318 Atarah Plain Leather Ballet Flats, Women's Size 11M, Gold , Ladies Clarks Formal Brogue Style Shoes Dawson Reel , Josef Seibel black leather clogs mules slides Size Sz 39 8 , Minnetonka Womens twill junior trapper Closed Toe, Silver, Size 7.0 fDeSWoman's peas leather shoes,Bow tie tassel casual comfortable light ladies shoes , FRYE Sneakers Canvas Slip Ivory White Weather Look Size 7M , Drew Motion sz 10xw Casual Black Leather Sneaker Shoes Women's**Sam Edelman Danica Mules, Women's Size 9.5 M, Gold/Blue , Naturalizer Womens Saban Brown Leather Loafers Shoes 7.5 Medium (B,M) BHFO 9921 , Multi Stripe Surf Beach Slip On Flip Flops Sandals Slippers /Merrell Thermo Black Leather Waterproof Vibram Womens Shoes Size 6.5 EUCNike Revolution 2 Women Black Pink Blue Running Shoes Sneakers Size US 11 , Vtg Light Purple Converse Hitop Chuck Taylor All Star Tennis ShoesMERRELL Moab Continuum Waterproof Hiking Shoe Womens Size 7.5 Gray Outdoor Sportadidas Cloudfoam Advantage Adapt - Grey - Womens , K-Swiss X Lite Cross Training Sneaker Shoe - WomensNike Air Max Thea SE Women's Shoe Metallic Hematite 861674-002 size 7.5NEW BALANCE WOMEN'S FuelCore Agility v2 WXAGLSM2 Cross Training Shoe Size RP $90 , Custom Fashion And Comfortable Women Boots Owl Martin Boots For GirlConverse Chuck Taylor All Star Dainty OX Women's Shoe Red/Black/White 555987c , EUC Nike Zoom PEGASUS 31 Hyper Pink Running Shoes 654486-600 SZ US 10 WOMEN'S A6Zoot Sports Del Mar - Black - Womens , Women's Nike Air Force 1 AF1 Metallic Purple Sneaker (7.5)Adidas Hardcourt Hi Sneaker Vivid Pink and Blue Women SIZE 9Womans Vans Oldskool sizes 6 - 10 baby blue , Aldo Womens Forema Sneaker- Pick SZ/Color. ,
"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."