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.JBU Wildflower Flats Sandals Red Women Size 8 Mary Jane , Calico Women's Black Suede Studded Flats Loafers Shoes Size 6 1/2 MBOBS Skechers 34987 Instinct Zebra Canvas Loafer Slip On Womens Size 8.5Skechers Women's Cleo Rattler Ballet Flat Black 5 M US , FootJoy GreenJoy Womens Golf Shoe Size 8 M Oxford White Leather Style 48812 , CORSO COMO Size 7.5 M Black Suede All-Leather Zipper-Detail Gorgeous Ballet FlatWurl Landry-Women's Brown Shoes 6 1/2 MWomen's Sam Edelman Farrell Taupe Suede Slip-on Moccasin Shoes Size 8.5 M** Rieker D1912 Malea 12 Slip-on Shoe, Women's - Size (US 8.5-9), SlateARRAY Womens Freedom Leather Square Toe Loafers Navy Size 9.0 nwZWKLOGS ODESSA WOMEN'S DISPLAY MODEL SHOES MUSTANG COPPER 9.5 MWendy Williams Black Animal Hair Leather Fashion Sneakers. Size 8.5 M,ENZO ANGIOLINI OMANIE Taupe Fabric Designer Flats Comfort 8.0 M , ADIDAS FEMME TORRA NOIRES ET BLANCHES T 36 A € ACHAT IMMEDIAT LIRE ANNONCESteve Madden Saam flats black open toe sz 6 Med NEW , Marc Fisher Women's Abree Loafer Flat Black Size 7.0 fIhW , Vibram Five Fingers Barefoot Minimalist W138 Shoes Size 39 Black / YellowSaucony Womens Zealot Iso 2 Silver/Mint/Coral Running Shoes Size 9.5 (366372)Nike Vapor Court Tennis Shoes White Aqua Tennis Shoes Womens Sneakers Size 10 US , Reebok Women's Trainflex Cross-Trainer Shoe, White/Skull Grey/Metallic SIZE 7.5Women's Naturalizer Women's Cypress Flat Characteristical Athletic ShoesJambu Women's JBU Wildflower Flat , WOMEN'S NIKE ZOOM ELITE+ 6 SHOES SIZE 11.5 blue silver anthracite 554728 400Mizuno Women's Wave Bolt 4 Ankle-High Running ShoeWomen's Reebok Ziglite Run Running Shoes Black Sports TrainersDce Vita Tillie Knit Sneaker Sz 9 M Grey MeshSoftWalk Murietta? size 7.5W Clogs Mules Shoes Rust Bronze Embossed side buckle , Caleres Inc Variation Ryka Womens Dream Training Shoe- Choose SZ/Color.Soludos Womens Pink Platforms Fashion Sneakers Shoes 9 Medium (B,M) BHFO 9172 , Skechers Black White Shape Up Shoes Size Women's 9.5 Athletic Sneakers Walking ,
"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."