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 LAUREN CONRAD Dex CORAL 6.5 Scalloped Cutout Ballet Flat , NWT Black Leather/Fabric NaturalSoul by Naturalizer7 M Classic Loafers, Nice!OLD NAVY FLATS ROUND TOE PERFORATED MAN MADE SLIP ON NON SKID SOLE TURQUOISE 7 , Women Dockers Olive Leather Low Heel Loafer Mules Size 7 1/2 Med. "DkMedfordk" , minnetonka kilty suede moccasin Pink 8Stuart Weitzman Quilted Cap Toe Chain Ballet Flats Legacy Womens SZ 8 WorkNaturalizer Women's Kaz Round Toe Loafer, Black, Size 8.0-DisplayZUMFOOT LEATHER SHOES ARCH BACK SUPPORT US 11 - 11.5 HOT UNIQUE RARE , Sam Edelman Womens Metallic Gold/Multi Color Flats 6 M , Vince Camuto Silver Gold Sz 8.5M Cut Out Flats Slight Heel Cute!occdient womens Trainer Atheletic Sneaker Unisex size black 7Merrell Women's Trail Runner Mix Cross Trainer Yellow Aqua 9.5 Water Resistant Z , Women Ladies Leather Oxfords Flat Shoes Casual Slip On Loafers Soft Comfy Shoes , Ralph Lauren Womens 9.5 B Brown Leather/Fur Moc Slip Loafers Trudy ALW 57586~143Vans Authentic Slim Checker Kaleidoscope Women's 5 Kids 3.5 Black White New Shoeleisure fashion Flats sneakers Loafer Round Toe Slip on Breathable Womens ShoesMen's Robert Wayne Highway Slip-on Loafer, Dark Grey, 11 MWide Fitting Navy Mens Slippers Machine Washable Booties Size 6-12SKECHERS 12370 SRR RESISTANCE SHAPE UPS Womens Black Sneaker Shoe 7.5 M Work OutNew Under Armour Women's Street Encounter Sportstyle Shoes - Size 8 - Baja , Nike Cortez Nylon Hyper Pink White Juniors Girls Trainers 749512 601Nike Revolution 2 Women's Running Shoe 554900 034 Size 8.5 , PUMA Women's Pulse XT Geo Cross Training Sneakers Ultramarine Size 8 M , NIKE DOWNSHIFTER 7 COOL GRAY/LAVA GLOW CORAL PINK RUNNING SHOE SZ 9.5,10, 9.5 M , New Sperry STS82398 Crest Vibe Washable Leather Grey Women's Boat Shoes 6.5 USNIKE INTERNATIONALIST Light Khaki Satin & Suede SNEAKERS Womens Size US 8Steve Madden White Slip on Giggy Silver Star Sneakers 9 NEW , Reebok Hexalite Womens Walking Fitness Shoes White Leather Sz 9.5D WIDEAsics GT 2000 Womens SZ 7.5 Running Athletic Shoes Sneakers Pink White Navy Blue , ECCO Soft Leather Sneakers RED Black Womens size Fashion Walking 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."