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's Born Brown Leather Clogs/Mules US 7 Sz Very Clean! Xcelent shape!Link Womens Canvas Slip On Double Tone Shoes College (Adults 6 7 8 9 10 11) , Propet Women's Wash & Wear Slip On Loafer, White/Navy Leather, 5.5 M US , Keds 7 Navy Red Slip-On Tennis Shoes WF23376M B3-CH59 , AEROLOGY FLEX, by AEROSOLES women's shoes, slip on, size 9 suede, light brownChinese Laundry Women's Easy Does It Flat.,Dark Teal,6.5 M USNew L.L. BEAN Red Leather Handsewn Slip-on Shoe Loafer Womens 9 , B.O.C. Born Concept Brown Leather Women's Shoes/Clogs Size 8M , Dooney&Bourke Paraboot Blue/Brown Nubuck Leather Moccasin Boat shoes, sz.8 (US)Cole Haan Womens Eudokiasam Closed Toe Ballet Flats, Purple, Size 6.0Mephisto Runoff $260 Air Jet Women's Oxfords Shoes Size 6.5 Nubuck Leather BrownAcorn Women's Acorn Moc Tex/Polar - Navy Popcorn - S , C20 NEW Mercer Edit Callback White/Silver Leather Low Top Sneakers Women's Sz 10 , ASICS Women's GEL-Volleycross 3 B150N. Volleyball Shoe,White/Red/Silver Size 9 MCONVERSE ALL STAR SNEAKERS WOMENS SHOES SIZE 7 BLUE PURPLE COSMONew! Women's Skechers 14317 Go Step: Solution Walking Shoes - Navy O67 , Comfy Feet Happy OFFICIALLY LICENSED Mens and Womens NFL Sneaker SlippersSaucony Womens - Mint/Blue Running Shoes Size 8 (345140)Reebok Shoes Women's White Size 10.5Women's SKECHERS GOTRAIN Gray/Pink Comfort Athletic/Walking Shoes 14830 NEW , Women's Lorraine Women Canvas Sneakers Shoes Terrific Value Athletic Shoes , Asics Walking Shoe Gel Frequency 3 Navy & Mint Women's 9.5ECCO Women's Exceed Low Walking, Mauve, 41 EU/10-10.5 M USNIB Puma Women's Voltaic 5 Pink/Blue/Silver/Lime Running Shoe 187346 , SUPRA WOMEN'S SKYTOP BLACK GOLD WHITE WOMEN SHOES SIZE 5Women's Nike Free 5.0 White Black Shoes -Size 6.5 -724383 100
"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."