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.WOMEN SHOES ROS HOMMERSON SANDALS Size 7.5W BLACK LEATHER NEWSuper Cute Clarks Women's Flats Size 7 BLACKBNWT Older Girls Sz 4 Rivers Doghouse Brand Blue with flower slip on Canvas Shoe , Women's Clarks Gael Bobtail Slip On Shoes Style 15260 Brown Size 6W , Aerosoles Womens hey girl Pointed Toe Ballet Flats , Women’s Sz 11 Asian Woven Shoes Flats Leather Maroon Moraccan VelvetESPADRILLES P. 39 PICHOTO "Né en Provence, Fabriqué en Espagne " PRIX MAGA , Women's Cole Haan Grand Os D43391 Moccasins Loafers Shoe Size 9B Pink Leather O2Blowfish Womens Carter Black Casual Shoes Sneakers 6.5 Medium (B,M) BHFO 2134Palladium Low cut women US 5.5 Leather Grey Fashion Sneakers Pre OwnedMen Low Top Casual Canvas Shoes Sneakers Breathable Rubber Flats Running ShoesNIKE FREE RUN 2 ID "TINA" WOMENS 7.5 EUC SUPERCLEAN RED BLU TEALsee pics-detailsSAS Free Time Womens Leather Oxfords Walking Shoes Size 10 S Tripad Comfort , Asics Womens US 7.5 GT-1000 Athletic Running Shoes Blue T7A9NNEW Saucony Cohesion 4 Womens Size 9.5 Running Shoes Gray/Silver/Pink ~ MINT! , Diadora Kuruka - Black - Womens , Women's Asics FuseGEL Womens Beautiful Design Athletic ShoesNike Women's Roshe One Flyknit Shoes NEW AUTHENTIC Orange/Mango/Sail 704927-802 , NIKE Women's Free Transform Flyknit Training Shoe size 12 Mica Blue 833410 403Adidas Originals X Pharrell Williams Pw Tennis Hu Women Ash Green DB2557 , Ice Vizsla Dog Print Running Shoes For Women-Free ShippingBrooks Glycerin 15 Blue/Purple Running Shoes Women's US Size 6 (F1,1)OTBT Green Lake Havana Cold Weather Boots - Leather Flatform Sneaker - 7 M -$135**Steve Madden Giggy Slip On Sneaker, Women's Size 10 M, BlackWmns Nike Roshe Two SE 2 Gold Pink Women Running Shoes Rosherun 881188-700CONVERSE CT PC2 MID Drizzle Grey Textile Trainers 141701F , MBT Womens 9.5 / Mens 7.5 Brown Leather Athletic Walking Shoes Toning - Superb! , Calvin Klein Womens Slide on Shoes Valette Black W/White 34E9807 Size US 8 , SKECHERS Memory Foam Women’s Wedge Shoes, Black, 6 Eur 36. ....S38 , Nike Air Max Womens size 8 Vintage White Blue Silver All original 105132
"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."