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.KS35 Ralleigh Studded Ballet Flats 621, Black, 7.5 W USMovmt Katie Women's Black Textile Slip On Loafers US Size 6.5 , LIZ CLAIBORNE GOLD & BLACK LEATHER SNAKE LOW HEELS WOMENS US 8 MMarc Jacobs Women's Blue Velvet Round Toe Slip On Ballet Flats Size US 7 , Sperry Top Sider Womens Shoes Sz 10m Pink Chunky Glitter Sparkle (43)**Natural Soul Girly Flats - Women's Size 8W, Black , Sperry Boat Shoes Cheetah Print Womens Size 6.5 , Nine West 25028643 Womens Alberry Loafer- Choose SZ/Color. , Prada Women's 36 6 Olive Green Brown Leather Platform Loafers Shoes Velcro VGUCNEW SKECHERS WOMENS DYNAMITE FLEETLY COMFORT MEMORY FOAM SLIP ON SHOESROBE SEE BY CHLOÉ SOIRÉE 36 FR NEUVE SOIRÉEStuart Weitzman 5.5 Gray Wool Buckle Square Toe Slip On Career Flats Shoes PumpsSam Edelman Women's Leya Faux Fur Pom‑Pom Slip‑On Sneakers - Size 8.5 M, PinkDr. Scholl's Vienna Slip On Shoe - Women's Size 8.5 M, WhiteNew with Box Ann Taylor Alta charm suede Flats 9 dark burgundy Red $118ASICS Gel Flash T2J5N Running Cross Training Shoes Size 8 GREATNew! Women's Skechers VASO Full Grain Leather Sneaker Style 48865 Cognac W78 rt , Dune London Grey Women's Black Slip-On Loafer 7M , Hotter Women's Abbeyville Shoes Maroon GG8 Size 9.5New Balance Barringer 890 Black/Purple Athletic Sneakers Women's Size 9.B , Nike Air Women’s Walking Shoes Silver Rolling Rail 315264 Size 9.5 , Vintage MICR Womens high-top White & Navy Sneakers 7.5 MWOMANS BRAND NEW WHITE LEATHER SKECHERS SPORT TENNIS SZ 10 ATHLETIC SHOESNEW Womens Size 7 NEW BALANCE 624 AB2 Black Synthetic Leather Sneakers Shoes , ASICS Alvarado - Black - WomensMBT Womens 41 US 10 SNEAKERS SHOES Toning WALKING Shapers BLACK Athletic WNew Balance Women's Wcoas Suede Running Shoe , New Balance Women's W775V1 Neutral Running Shoe, Silver/Pink, 5.5 B USdc women's rebound high fashion sneakear,white/purple 7,7.5 & 10 M US , Clarks Collection Mary Janes Brown US Size 9 M - FREE SHIPPING - BRAND NEW
"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."