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.Softspots Women's Stephanie II Wedge Grey Size 7M , Rockport XCS Slide Sandals Women's Size US 9 SlippersSAS Tripad Comfort Black Leather Slip on Loafer Sz 9.5 S N MSRP $145. VGUC!Soft Style Faeth Flats - Women's Size 7, Black , Great Northwest Clothing Company Womens Black Leather Mule Size: 8Nurture Womens Grey Leather Slip On Mules Shoes Size 6.5 , Enzo Angiolini Women's Blue Admond Boat Shoes size 8.5M 41518-3 S1AEROSOLES METALLIC LIGHT PURPLE LAVENDER LEATHER COMFORT BALLET FLATS SIZE 9 , Pleaser Daisy Flat Demonia by Womens Daisy-04 Mary-Jane Flat- Choose SZ/Color. , Born Brown Leather Platform Slip on Mule Clogs Loafers w Contrast Stitch 6MEasy Street Mischa Casual Flats - Women's Size 6.5 M, TanWomen's ELLEN TRACY Cheetah Flats Size 6.5 M , WHITE MOUNTAIN Women NWOB Size 7M Black Slip On Clog Soft Fleece Accent Comfort , NIB SPERRY JEFFREY CVO ZEBRA PONY HAIR SNEAKER-RETAIL $100 , Foot Petals Cami Ballet Flat - Women's Size 7M, Black , ASICS Gel-Storm Running Shoe Pink Orange Yellow T3N5Q Size Womens 10Brooks Adrenaline GTS Womens Gray Blue Running Shoes Size 6 B MediumConverse All Star Women's Sz 5.5 Gold Metallic Black Zebra Hi Top Sneakers (P) , Nike Free Run 3 Black Running Shoes Pink Force Blue Reflect Size 8.5 WomenNew Balance 413 ABZORB Running Shoes Sneakers Womens 7.5 CW413WO Yellow white , Raulph Lauren Polo Women’s Boat Canvas White Shoe 8M , Vivobarefoot Women's US 6.5 Eu 37 Purple Gray Trail Running Barefoot Shoes , Avia Taupe Volante Country Walking Shoe Womens Size US 8D New In Box , Converse Men's / Women's Chuck Taylor All Star Summer Woven Ox Shoes Black , Tibetan Spaniel Print Wallet Case-Free Shipping , MISMATCH Size L-7.5 R-8.5 BROOKS PureFlow 2 Running Shoes Diva Pink Black SilverNike Shox Women’s 7 Black/Purple White Spring Athletic Running Shoes 356918 , ASICS Womens T689n Black/Black/DivaPink Running Shoes Size 7 (326301) , Marc Fisher Women's Barbora Espadrille Natural/White Woven Fabric Platform Shoes , Vans AUTHENTIC LO PRO Gossamer Green/White Women's Shoes 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."