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.Innovations Jamie Brown Leather Slip On Comfort Chunky Heels Shoes Size 8 , DC Women's Venice LE Casual Shoe White Size 7.5WLadies Spot On Slip on Ballerina Shoes with Bow Trim & Stud Detail F8864Moccasins sz.5M flats black suede/leather Country Lane career comfort Mexico EUC , NWOB BORN Womens 8.5 Red Suede Slip On Flat MoccasinsDANSKO Womens Vegan White Tan Mary Jane Comfort Clogs Size 40 9.5-10EARTH Beetlebug Moss Brown Leather Slip On Comfort Shoes Women US Size 12 BWomen's Aerosoles Flats - Betunia - Black Snake - New in Box! , Aerosoles Women's Upper Level Flat, Blue Combo, 6 M US , CC Resorts cloud comfort Chris - Athleisure walking shoe , Women Dragonfly Accessories Loafer Wedge Heel Platform Low Top Leisure Shoes , BCBG Max Azria navy blue comfort ballet flats shoes size 40 Made in SpainClarks Candra Blush Ballet Flats, Aubergine, 9 US / 40 EU , EUC Cole Haan Gilmore Black Perforated Suede Ballet Wedge Size US 8B Flats A6 , New Calvin Klein IMILIA CK Logo Flower Print Brown Womens 6 M Sneakers Shoes $99Cole Haan air black patent leather ballet flats buckle shoes pump 9.5 , NAUTICA Women's LUBEC Mid-Fashion High Top SNEAKER - Size 8 - Black - LW0021 , 02-1457 MEN'S Tretorn Tournament Net For J.Crew Sneakers (Size 8MNike Women's MD Runner MID Hi Top Trainers Running Sneakers Shoes US 9Puma X Alexander McQueen Jogger Shoes 357760 01 Size 9.5 Women’sNew Merrell J09654 Bare Access Flex Paloma Women's Running Shoes 11 US , NIKE Air Zoom Elite 9 Womens Running Shoes Sneakers Pink Black 863770 NEW SIZE 7 , Skechers Women's ONE Bora Exalting Sneaker , VIONIC Orthaheel Ailie Mary Jane Athletic Shoe White, Pink, Grey Sz 11 NWOBRIGHT SHOE ONLY NEW BALANCE Women 7 Summit Textile Olive CW620LA - SAMPLENike Womens Nike Freefocus CoolGrey/WolfGrey-hyperVolt-summitWhite Running Shoes , Avia Avi-Versa A5569W-SHN Cool Mist Grey White Frost Mesh Running Shoes Women , Nike Kawa Slide Women's Gunsmoke/Crimson Tint 34588002Vintage Nike Womens Contagious Sneaker WMNS 6 Blue/silver/black/yellow 171105-43Original Kitson Sketch 34500 TAN Prima Donna Casual Women Shoes ,
"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."