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.Thalia Sodi Jaci Ballet Flats 846, Black, 7 W USSoft Style Women's Faeth Denim Flat 6.5M , Clarks Collection Women’s Black Leather Clogs Size 7/37.5LifeStride Women's Fantell Ballet Flat, Mushroom, 7.5 W USNaot Womens Heels Loafers Black Color Size 36Women's SAS Simplify Loafers Shoes Size 11.5S Red Leather Tripad Comfort USA AC1 , G.H. BASS & Co. Jenna Espadrille Women's Size 7 Flat Slip-On Shoes Blue/PinkSperry Top Sider Womens Tan Angelfish Eye Casual Loafer Boat Shoes Size 6.5 , Mojari Indian Handmade Women Leather Shoes Ballerinas Flat US 6 , Life Stride Deliberate Black Patent Women Shoes Sz 7.5 W AL4067$80 size 6.5 Anne Klein Uplift Pewter Ballet Flats Loafers Womens Shoes , Women's Skechers 14914/BKW Go Walk 4-Fascinate Black and WhiteCole Haan Women’s Brown Leather Slip On Casual Sandals Mules Size Sz 8 B , GEOX Wo's 8 Eu 38.5 Black Patent Croc Embossed Rhinestone Horsebit Loafer , NEW GRASSHOPPERS Burgundy red Velveteen Shoes Flats Loafers 6- 6.5 6 1/2 W Wide , Klogs Clara Women's Leather Clog Display Model Shoes Mustang 6 MJack Rogers Caroline Suede Ballet Flat, Women's Size 7 M, BlackSperry Women's (Sz 7) Seacoast, Canvas Sneakers, Charcoal, (3274P)Adidas Womens CF Lite Racer So W Slip On Comfort Shoe Blue Pick A Size , Nike Free 5.0 TR Fit 4 Print Womens Running Shoes Green Yellow Sz 9.5 629832-302K-Swiss Flow Cool System Women's 8.5 Running Training Tennis Shoes White GoldSaucony Womens Size 10 Blue Grid Cohesion Running Shoes , Earth Origins Carly 8.5 W Wide Womens Blue Suede Slip On SneakersVionic Venture Athletic Shoes Women Size 9 , Womens New Balance W580LG5 580 Reflective GREY Neon Green Comfort Running ShoesTruffle Collection Flatform Creeper Women SneakersSaucony S10355-3 Freedom ISO Blue / Citron Women's Running Shoes Size 7.5 NWT , New Balance Women's 300 Indigo Pack Lifestyle Fashion Sneaker Pigment/Sea Sal...MINT Brooks LAUNCH 4 Women’s Teal White Black Running Shoes Sneakers Sz 12 MMY.E Baskets Montantes Fourrure Synthétique Zébrée T 36 TTBE ,
"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."