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.Karl Lagerfeld Paris Womens Larose Beige Ballet Flats 10 Medium (B,M) BHFO 1795ppp ARIAT BROWN DISTRESSED LEATHER SLIDES WOMENS 8.5 B , Clarks Beige Leather Cutout Wedge Loafers Ballet Flats 10W 10 Wide MSRP $89 , Summer Flat Shoes Ivory Wedding Shoes Rhinestones Handmade Women Flats BrideGabor Womens Navy Leather Comfort Sport Oxford Shoes, size US 6.5 Eu 37.5 , Yellow Box Nicole Gunmetal Laser-cut Jeweled Slip On Espadrille Flats 9 NEWWomen's Paul Green Muchen Vibram Brown Suede Platform Loafer Shoes - Size 8M , CLARKS Artisan Black "Showstopper" Shoes, Active Air Heels, Womens Size 7.5M-B25 , Merrell 7.5 Beige Slip On Mesh Women's , Ladies Spot On Casual Canvas PumpsTretorn Olive Green Unisex Size 10.5 Fashion Sneakers Leather Sneakers ShoesNew Ghostbusters Logo Allover Hi-Top Sneakers Size US 7 Pre-orderKeen Ventura Gray Brown Tan White Vegan Women's Sneakers Size EURO 37, US 6 1/2Aerosoles Womens Smart Move Leather Closed Toe Slide, Bone Nubuck, Size 11.0 7gpPuma Roma SL NBK 2 Blue Fluorescent Purple Turbulence 355494 01 Womens Size 9 , Isotoner A91338 Moccasin Slippers - Men's Size 9.5/10.5, Black , Merrell Zeolite Serge Stone Purple waterproof air cushion hiking boots Womens 8 , NEW Nike Women's Air Max Mixer Mid Size 10.5 Black White Red? Vintage RareSaucony Womens Jazz Original Pink Fashion Shoes Size 8.5 (354115) , Reebok sz 7M Zig Nano black running womens ladies sneakers athletic shoes , KEEN Toyah Mary Jane Brown Leather Rubber Toe Casual Comfort Shoe Womens SIZE 8ADIDAS ORIGINALS Women's BZ0412 Stan Smith Multi-Color, size US 6 RARENike SB PAUL RODRIGUEZ CTD LR (GS) 677375-014 YOUTH SZ: 5~7 WMN SZ: 6.5~8.5 , Cynotilapia Afra (Afra Cichlid) Fish Print Christmas Running Shoes For Women- Fr , Skechers Go Walk Move-Afterglow Outdoors Women's Shoes , Nike Women's Air Max Trax Running Shoes size 7 style 631763-101 , SKECHERS BLACK WHITE MEMORY FOAM GEL TENNIS SHOES WOMENS 8M 8 NWT ~ FREE ship!New Balance Women's Wl628 Low Top Suede Fashion SneakerECCO Womens Terracruise CapriBreeze/Aquatic Trail / Hiking Shoes Size 7 (327394)New Helly Hansen Women's Running Shoe Size 7.5 MSRP $120 ,
"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."