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.Taryn Rose Tutu shoes womens size 8.5M gray fabric loafers comfortClarks Indigo Women's Black Patent Leather Heelp Pump with Bow Shoes Size 10 MKEEN indoor/Outdoor Womens US SZ 11 Clog Shoes Tan Leather Casual Loafer GUCJOSEF SEIBEL Black Leather Slip On Loafers, Dual Elastic Gores, Size 37, VGUCClarks Artisan "Berwick Ave" Brown Leather Mock Buckle Heeled Loafers Sz 5.5 EUCClarks Womens Brown Leather Mules Shoes Size 8 , LL Bean Gray Pink Lakeside Boat Shoes Loafers Size 10 , STUART WEITZMAN Ladies Black Suede Flats Size 8.5M , NWOB Nine West Suede Flats Shoes 12 12M 12B 42 NEW , Women's Easy Spirit "Take It 2" slip-on clog shoes light grey - Size 7m , Ladies Easy B Canvas Shoes Hanna , RARES CONVERSE ALL STAR ECRUES BE T 37 A ACH IMM FP RED MOND RELAY TOP , NWT CHARLOTTE RUSSE Star Print Low-Top Canvas Sneakers Faded Blue Americana ShoeHigh-Elastic Cushioned Gym Shoes Slippers Women's Workout Yoga Dance Polyurethan , PRIVO Clarks BROWN Tan Leather Mary Janes Loafers Casual Comfortable Shoe 10 MFranco Sarto Womens dalton Suede Closed Toe Slide Flats, Black, Size 9.0 Db7Eadidas originals samoa g20682 women shoes white/silver 100% authenticNIB PUMA ROMA Metallic Women's Shoes 360977 01 Black-dark shadow Choose SIZE , BROOKS PURE CADENCE size 7B Women's Shoe Featuring PurpleMens Genuine Sheepskin Slippers Leather Home Warm Fur WoolSkechers Shape Ups Toners Womens Shoes Sz 10 Pink Gray Trainers -5294 , Propet W3902 Womens Leather Active Comfort Tour Walker Sneaker Shoes , Souliers Felycia suède noir Nine West grandeur 7.5 , Nike Women's Air Max Fusion Team Shoe Size 5.5 (578353-007) WOLF GREY/BLUE , Shoes Skechers OG 84 Rise n' Shine Sneakers 820 bkmn Womens Black Mint Casual , Under Armour Womens Charged All-Around Neutral Lifestyle Shoes- Pick SZ/Color. , Newton Motion V Women's Running Shoes Peach US Size 11.5 (E1,8)Nike DOWNSHIFTER 8 Womens Black White 908994-001 Running Athletic Training Shoes , Converse Chuck Taylor Gel Hi High-Top Canvas Sneaker Raspberry Size US 6 , EUC WMNS STUDIO TRAINER 2PRINT BLUE 684894 008 RUNNING ATHLETIC SNEAKERS US 9.5
"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."