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.BLACK HAWK BLACK COMFORT CLOGS SHOES SIZE 4 SANDALS BIRKENSTOCK , Life Stride Black Mary Janes 7.5 , Women's Shoes by Naturalizer size 6.5M, Brown Leather Upper Pant Shoes, 2" Heel , Ladies Savannah Silver Sequin Flat Shoes UK Sizes 4 - 7 F80070 , New Women Alfani Argent Round Toe Synthetic Gold Flats Summer 9 Shoes MSRP$59.50 , FEMMES (DB) BLEU CIEL/ BLEU CLAIR CHAUSSURE CUIR "AMBRE"POE Carin Light Pink Iridescent Leather Beaded Ballet Flat 7.5 NewJutti Women Shoes Leather Flip-Flops Designer Indian Oxfords Mojari Pink US 6-9Sperry Top Sider 2 EYE Black Women's Shoes Slip-on Sneakers Size 6.Gant New Haven Cotton Bone Beige slip on sale 14579595LADIES CLARKS CLOUD STEPPERS SLIP ON CASUAL WEDGE PUMPS SHOES SILLIAN JETAYCole Haan Womens Sadie Deconstructed Shoes Size 10 B Teal Flats D40331Women's Nike Walking Shoes White and Gold Size 7.5 , Women's Running Casual inside Heightening Shoes Air sport Shoes Athletic Sneaker , Cabela's Women's Wilderness GORE-TEX? Hikers SZ. 8 M , WOMEN PREOWN TOP QUALITY "NEW BALANCE" RUNNING/WALKING TENNIS SHOESGRAY-sz 9 , New! Women's Skechers 22692 EZ Flex 2- Joy Ride Slip-Ons Natural A32 , Ladies Chalsie Prissy Red By Marc Ecko Sz 10 High Top Canvas Basketball Shoes , Hi-Tec Women's Hiking Sneakers Boots Shoes Suede Fabric Brown Grey 8.5Asics-GEL-Enhance Ultra 4 Running Shoe, Women's Size 8, Black , Easy Spirit Women's Enoris First Walker Shoe, Grey, 8.5 M USAdidas BB8081 Aspire Tennis shoes black white pink SneakersVans Womens Era 59 C&L Sneakers Dolphins True White Size 9.5 New , Inov-8 Women's Roclite 290 Trail Runner, Grey/Pink/White, 8.5 D USRyka Sport Walker 6 Walking Fitness Athletic Shoes Sneakers White Blue Womens 10Demonia Women's Cramps 03 Ankle Strap , NEW K-SWISS WHITE LEATHER COURT CLASSICO SNEAKERS SHOES TRAINERS SZ 10 , Nike Dualtone Racer Womens Sneaker Purple Black Running Training 917682 604 NIBSkechers BOBS Women's Bobs Swift-Zap Zing Fashion, Black/Turquoise, Size 9.5MBT Womens Wave Walking Sneakers Comfort Toning Rocker Light Blue Suede Size 7
"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."