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.Vince Suede black espadrille slides size 37 or 7.5 , Spot On Black Ladies F8634 Great Fashionable Flat Shoe (7A)Merrell Dassie Slip-Ons-Women's size 11 Black(Damage)SAS Tripad Comfort Women's Easier Mocha Slip On Wedge Loafer Size 9 M , Aerosoles Women's "On Call" Black White Stitch Buckle Kitten Heels Size 7.5M USGrasshoppers Women's Black Slip on Casual Shoes Sz 8 W C821 , 81 Paul Green Pacific Rosewood Suede Bow Cutout Flat Women's Sz 5.5 USRieker Women's Slip-ons Ballerina Low Shoes Court Shoes Multicolour 537a5 NEWNike Light Blue Women's Size 9M Air Max Sasha Low Top Walking Shoes $75- 181Nike Free Run Tennis/Athletic Shoes Size 6 Youth PreOwned Black/Lime Green , NIKE W AF1 REBEL XX OFFWHITE AO1525 100 ATHLETIC BASKETBALL WOMEN'S SIZE 6 WB , Naturalizer Womens Manor Black Fashion Sneakers Shoes 6 Medium (B,M) BHFO 3947 , Women US Shoe Size Slip On Elasticized Ballet Flats Sandals Casual Navy Blue NEW , DC Womens Chelsea SE ShoesB- Pick SZ/Color.Asics Women's Gel-Cumulus 17 Athletic Running Shoe Pink Green Size 9.5MNike Women's Free 5.0 TR Fit 5 PRT Cool Grey/Flash Lime/Blue Lagoon Size 5.5M , WOMENS ECCO LEATHER FASHION SNEAKERS SIZE 40 GOLFWomen Brooks Glycerin G13 Running Cross Training shoes size 7 USBrooks Ghost 5 Athletic Jogging Training Running Shoes Womens Sz 7.5 US BlackWomen's Air Force 1's Modern Design Athletic ShoesConverse Chuck Taylor All Star Ox Womens 157651F Raw Sugar Canvas Shoes Size 7New Adidas BZ0593 Terrex Swift R Grey Women's Hiking Trail Shoes Size 9.5 USWOMEN'S NIKE AIR ZOOM PEGASUS 34 SHOES SIZE 5.5 blue black white 880560 400 , Women's Nike Cortez Ultra BR Shoes NEW Green/White New. , NEW NIKE Presto FLY SE Women's Running Training Shoes AA3060 002 6Y US 7 24 cmMizuno Wave Rider 19 Running Shoe Grey/Teal Women's US 10 Eur 42 (L3,20)NEW! Womens Skechers 14148 Go Walk 4 Walking Slip-Ons Black/White R18 , ADIDAS NWT White/Black Excelsior 5 W Low Metal Cleats Softball Shoes sz 12Skechers Shape-Ups Leather Toning BKW 11809 Women's Size US 9
"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."