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.Lucky Brand Emmie Bronze Leather Ballet Flats Size 6M , NEW WOMEN'S LANDS' LANDS END SLIP ON SHOE SIZE 6 M SUEDE GREEN SIDE BUCKLE , LADIES FLAT ELASTICATED CANVAS SLIP ON CASUAL SUMMER PUMPS/ SHOES F8781AGATHA-02 New Synthetic Diamond Slip On Casual Women Flats Office Shoes SilverTommy Hilfiger Elsie2 Loafer Flats 905, Medium Brown, 7.5 USNew EURO SOFT by SOFFT Fondan Womens 6.5 M Brown Leather Loafer Reptile PrintSperry Top sider Bahama two-eyelet gray sequined boat moc loafer shoe 4M , Dansko Elise White Leather Comfort Sneaker Shoes Women's Size: 38 / 7-7.5 , Clarks Collection Women's Slip On Comfort Shoes - Size 8M - Black SuedeLands End Womans Flats Size 8.5 59356 Gray Block Heel Square Toe Mary Janes , Klogs Fairfield Women's Display Model Shoes White 8 MCrocs Women's Busy Day Strappy Flat - Choose SZ/Color , Bass Weejuns Peggy Mule Slide Penny Loafers Womens Size 9 M Black Shoes Brazil , Natural Soul Women's Carryon Slip-On Loafer Shoe TW4 Black Size 9W $74SKECHERS WOMENS FLEX APPEAL 2.0 HIGH CARD /GRYMerrell Women's Wild Dove Gray Trail Running Shoes J56352 SIZE 7.5 , Womens Nike Training Running Dual Fusion 7.0 Athletic Tennis Shoes Hot Pink/Gray , SKECHERS DLITES Womens Running Shoes Leather Pink Gray Sneakers Size 8.5Hot Womens Embroidery Floral Hidden High Heels Sneakers Casual Creepers Shoes , Stafford Men’s Size XL 11-12 Taupe Memory Foam Slippers Brand NewRockport Thurston gore 8.5 WomenUzzy Main Stage Sneaker Slippers Plush Unisex WhiteREEBOK HEXAFFECT RUN 2.0 V66087 CORAL PINK BLACK RUNNING WOMEN SIZE 7Asics Gel ENDURO 7 Women's Running Shoes T1G5N Gray/Green US Size 7 , Women's Naot women mules 41 New Varieties Are Introduced One After Another Flats , Lacoste Carnaby EVO 118 3 SPW Trainers in White & Light Purple & BlueWomen's SperryMaya Pewter Slip on dress Boat shoes Stk color PewterNewton AHA Women's Running Shoes Size US 9.5 M (B) Purple W004214B , Stylish Sheep Curls Women Shoes Comfortable Platform RounToe Sports Loafer ShoesLANTINA Women’s Low Top Fashion Sneakers Canvas Shoes Lightweight and Breathable ,
"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."