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.TS shoes TAKING SHAPE sz 6 / 37 Paloma Pool Slide comfy easy wear slip-on NIB! , New Flat Women Comfortable Loafers With a Buckle -Black xflBB: BEAUTIFUL BROWN WOMEN'S SHOES SIZE 6 by ANNE KLEIN , Aetrex Mary Jane Slip On Black Size Elastic Stretch Leather US 9.0 MedARRAY Womens Closed Toe Loafers, Black, Size 9.0 2rVq , Mojari Handmade Leather Women Shoes Indian Flip-Flops Ballerinas Flat US 6/7New Bandolino 40 9M womens loafers dark green patent leather buckle flats , LOGO by Lori Goldstein Vicky Black Mesh Comfort Walking Athletic Shoe Size 8MNEW Naya Elle Black Leather d'Orsay Flats sz 10 Shoes Sandals D2550L1 , $60 Converse Womens Size 7 Chuck Taylor All Stars Gemma Slip On Shoes Tan White , Women’s Keen Mary Jane Loafers Burnt Red Suede Leather 7 MMERRELL ENCORE WOMENS US 8MADAMS DARK EARTH SOFT SUEDE LEATHER MOC SHOE , Womens TRAVELSMITH White Leather Mary Janes Loafers Shoes Flats SIZE 6 M ~NICE~Superb ENZO ANGIOLINI Brushed Silver/Gold Loafers w/Gold/Silver Stars - 6.5MRose Petals Foster Black Fabric Leather Trim (Women's) Size 8 1/2 N, NWB , Skechers Women's Flex Appeal 2.0 Walking Sneakers Size 8 , Keds Women's 7 Brown Walnut Sportive Suede Athletic Classic Round Sneakers Shoes , Skechers BOBS from Women's Chill Luxe Flat Brown 8 B(M) US , ECCO Women's Monk Strap Brown Leather ~Sz 39 /8.5 USNike Flex Trail 2 Women's Running Shoes Size US 8 Blue 616681-402 , New Balance Women's Wx623 Cross Training Shoe,Black,8.5 B US , SAUCONY GLIDE 8 RUNNING SHOES - GREY BLUE PINK ( SIZE 8.5 ) WOMEN`SCONVERSE ALL-STAR Low Top Chuck Taylor Slate Blue Canvas Womens 11, Mens 9 , Women's San Marina pointure 38 Comfortable Feel FlatsWmns Nike Air Max Fusion Ttl Crmsn/sprt Trq-pnk Frc-ant 555161 800 Size 5.5 , Nike Classic Cortez Leather Shoes Black Sneakers Retro 398436 010 10Custom Comfortable And Fashion Women Colorful Skull Boots Martin Boots For Girl , New FILA Women's Gym Athletic Shoes Sneakers Coolmax Memory Foam , Skechers Women's Bikers Totem Pole Chukka Boot,Black,7 M US , Asolo Celeris GoreTex Hiking Shoes Size 9 Ladies Women Blue Orange Gray
"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."