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.✿ SOFTSPOTS Floral Cut-Out Tan Leather Pillowtop Comfort Flats 9.5 Wide L@@K!24 , Low Wedge Heel – Cute Office Casual Shoe - Easy Low Pump - 10Sanuk Women's Faux Fur Lined Slip On Loafers Beige Cream Size 6 , RARE Vintage Dr Doc Martens Womens Mary Jane US 9 Made In England T-Strapcrocs Women's Carlie Cutout Clog, Black/Black, 4 M US , Annie Shoes Women's Devine W Dress Pump, Metallic/Multi, 8 W USAlegria Dream Fit Leather Neoprene slip on Dena 39 chocolate , Salvatore Ferragamo Brown Leather Pumps Excellent Condition 7.5 AA Narrow , CLARKS Women's Dowling Pearl Walking Shoe Grey Synthetic Size 7.0 sPfw , Chic Womens Slip On Pointy Toe Flats Mules Bowknot Sandals Slippers Shoes CasualDr. Comfort Women's Therapeutic Diabetic Shoes Size 9 N Leather Upper And Lining , Naturalizer Stella Loafer 8 M Brown Leather New in Box , Brooks Ghost 9 Running Shoe - Women's Size 6 B, Azalea/Black (Repair)Nike womens sz 7 Lunarhaze running shoe purple and grey light weight , Merrell Womens Hiking Boots Mid Top Baja Ventilator Shoes Sz 7.5 M Walnut SuedeKangaRoos Womens Pink Green Running Cross Training Zip Pocket Shoes SZ 7.5 S111Womens Nike Free 5.0 TR Fit 5 Breathe Running Sneaker Shoes 9.5 , Nike Tanjun Running Women's Shoes Size 8 , Women's Asics Gel-Nimbus 17 White, Lime, Melon Running Shoes US 9Z-COIL WHITE SNEAKERS PAIN RELIEF LADIES 8.5 LEATHER SHOESPropet Women's Briana Croco Loafer , Women's Adidas Neo Cloud Foam Performance Lite Racer Running Shoe Active SZ 8.5NEW ASICS Women Gel-Fortify Running Shoe,Lightning/Turquoise T571N-9140 Sz 6.5Nike Womens Zoom Classic Cortez Pegasus 33 Shield Running Shoes 807471-101 Sz 10 , VANS ISO 1.5 (Mesh) Neon Purple UltraCush Lite Athletic Shoes WOMEN'S 9 , BROOKS CASCADIA 11 ANTHRACITE CRYSTAL BLUE WOMEN'S RUNNING SHOES 120204 1B 005New Women's Nike Free 5.0 TR Fit 5 WC Volt/White/Blue 803199-714 SZ 6.5-10New Skechers Sport Women'S Energy Sneaker,Black size 8 , Reebok Womens 11 Princess Classic White Leather Athletic shoes 107026361 ~58 , VANS Brigata Black/True White Skate Shoes MEN'S 7 WOMEN'S 8.5
"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."