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.Fergalicious Fergie Alana Black White Ballet Flats Loafers Shoes Size 7.5 cLOSeT , new womens dr scholl's georgia leather metallic slip on flats shoes size 6 , Christian Siriano For Payless Women's Pointy Toe Slip on Flats Shoes , Orthofeet Womens Sz 11 D Wide 817 Chelsea Black Leather Shoes MISSING INSOLESNaturalizer 7.5 Womens Brown Heaven Croc Print Buckle Loafers Flats , Diesel Pointy Toe 9 M Distressed Samba Sneakers Casual Ankle BootiesHotter Made in England Blue Nubuck Leather Loafer Retro Style #P8754 11 M EUCSperry Topsiders Brown Suede & Houndstooth Size 5.5 M EUC , NEW!! Calvin Klein Leta Beige Leather Loafers Flats Size 8.5M US 38.5M EUR , Naturalizer Womens Una Navy Embossed Flats Shoes 7 Narrow (AA,N) BHFO 0227Charles David Women's Oracle Penny Loafer, Black, 36 Medium EU (5.5,6,6.5 US) , STELLA McCARTNEY WHITE MENZIESSI RUNNER Sz 5.5Easy Street Women's Emma Fashion Sneaker, Cocoa Leather/Fabric, 7 WW US , Fila Fit Women's Walk & Sculpt Exercise Sneakers Black Leather & Mesh Size 8 M , Skechers Brown Suede Slip on Bungee Comfort Walking Sneakers Shoes 7Puma Pulse XT Sport - Clearwater-Blue Coral - Size 7Women's Ladies Rieker Flats M1356 In Many Styles FlatsMarc Fisher Macey Perforated Espadrille Platform Sneaker - Black - Sz 6 M , Adidas Campus W Womens DB1019 MINBLU,White,White Womens Size 8.5 , Converse Chuck Taylor All Star Hi Pale Coral Navy Womens Satin High-top Trainers , Custom Comfortable Women Boots Sonic The Hedgehog Martin Boots For GirlSuperga Women's 2750 Maufloralw Sneaker - Choose SZ/ColorUnder Armour women shoes 7.5 SpeedformVans Ladies Ward Rose Cloud Ladies Sz 7.5 new with box , Altra Torin 2.0 Zero Drop Women's Running Shoes Size 8 Grey Pink Preowned , NEW~Womens NIKE Tanjun Prem Fabric Low Shoes/Sneakers Black/Metallic Gold Size 6adidas Pureboost Xpose Women Running Shoes BB1733 Sz 7 USASICS Gel Cumulus 9 Running Shoes Women’s Size 6.5 US Excellent Plus ConditionSaucony Womens Caliber TR Black/Coral Athletic Shoe- Pick SZ/Color.Victoria WH7-125124_8 sneaker Women's - colour White US ,
"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."