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.NEW Womens SODA OBJECT PLAID Slip On Loafers PADDED Footbed Shoe SZ 7 , Rockport Women's Cobb Hill Lizzie Ballet Flat, Stone, Size 6.5 , Ladies Black Spot On Black Shoes F8598 , Natural Soul Vivian Casual Shoes - Women's Size 7.5M, Black , SAS "SIMPLIFY" BURGUNDY WOMEN'S SHOES FLATS 9N LEATHER COMFORT LOAFER SHOESDr. Andrew Weil Womens Loafers, size 9BDuck Head Size 8 1/2M Judy Shoes - BronzeFranco Sarto Women's Black Leather Flats 5 M , Women's Munro American Mary-Jane Black Synthetic Patent Trim Shoes Size 7.5 M , New SESTO MEUCCI Metallic Woven Leather Slip On Shoe US 6Born Winter Shearling & leather Clogs Brown Sz 10 , Cole Haan Brown Leather Buckle Flats Career Comfort 6 CUTE! , Naturalizer Black Leather Slip On Flats Loafer Textured Leather 8.5 M Comfort , Zara Black Velvet Embroidered Mules Flats in Size 7.5 US 38 EUR , Cole Haan Collection Black Leather Loafers Silvertone Chain Link Size 8 1/2 BConverse All-star Women's size 6 heathered jersey Multi White Pink Neon Hi TopLadies Spot On High Top Trainers F8958 , Dexter Women's Captiva Soft Toe Golf Spike Shoe White/Black Size 6.5MVANELi Womens agneta Closed Toe Mules Black Size 7.0GoldToe Men's Shoes Navy Blue Size 10.5D Memory Foam Insoles. T6Isotoner A9B998 Brown Micro-suede 360 Degree Memory Foam Moccasin Slipper w/Gore , Winter Men Slippers Soft Sole Autumn Warm Home Cotton Plush Indoor Flat Shoes , Under Armour Womens Speedform Gemini 3 Graphic Running Shoe- Pick SZ/Color. , STEVE MADDEN JAACKSON BLACK MULTI HIGH-TOP SNEAKERS SIZE 7 , adidas TUBULAR SHADOW - Grey - WomensNEW $120 Womens Puma Shoes Platform Lux Sneakers in Toreador Metallic Red sz 10Asics GT-2000 Solute Gel IGS US Shoe Size 8 1/2 Womens , Nike 807158-100 New Women's Speedlax 5 Lacrosse Cleats Shoes Size 6.5 White Gray , Roxy Womens Set Session Athletic Walking Shoe- Select SZ/Color. , NIKE Womens Solay Thong Print 882696-004 COOL GREY/WHITE Womens Size 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."