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.Earth Kalso Radius Black Suede w/Leather Accent Loafer Shoes Women's 6 B , 02-1590 SPERRY SEASIDE 2 TONE LINEN GREY WOMEN'S SIZE 6.5M , Women's 6M AEROSOLES Sea Salt Blue & White Denim Look Slip On Flats Sneakers , Taos Shuffle Womens Shoe Size 8 Brown Leather Slip On Wedge Pump Loafers G2SAS Womens Weave Slip On Wedge Loafers - Chestnut Leather - Size 10N$119 size 9.5 Calvin Klein Vrinda Black Leather Flats Slip Ons Espadrille Shoes , NEW❤️SEYCHELLES BLACK RED SUEDE TAN TRIM ANKLE STRAP BALLET FLATS-8❤️**Cole Haan Elsie Ballet II Flats, Women's Size 9 B, Snakeskin (DAMAGED) , Tahari Paulina Slingback Tassel Pointed Toe Loafers, Preppy Navy, 5.5 USALEGRIA Womens KELI Cosmic Multi Color Leather Loafers ; US 6-6.5 (KEL-753)Nike Zoom Pegasus 31 Athletic Sneakers Running Training Shoes Women Size 7 , Robert Zur RZ Womens Brown White Driving Moc Boat Deck Shoes Size 7 , Women's Dolce Vita Tux Slip On Sneaker Black Neoprene Size 10 , Womans Adidas tubular tennis shoe, size 8.5, eggplant , Vans Athletic Sneakers Gray Grey Canvas Purple Men's 8.5 Women's 10Munro Fashion Sneaker Women's Sz 8.5M Black Leather USA MADE (tu29) , Skechers 22602 BBK Women's air cooled memory foam flex black shoe new size 8Hi-Tec Women's Hiking Sneakers Boots Shoes Suede Fabric Brown Grey 8.5 , Puma narite teal yellow white shoes size 9.5 , 13507 Skechers Women GO TRAIN Size 6.5 Black/Hot Pink BKHPDansko Harmony Grey Suede Casual shoe NIB $110RARE? VANS x Disney Minnie Mouse Slip On Sneakers Pink Trim Sz 10.5 Wom - 9 Men , Sneakers and Athletic G by GUESS Jinny2 Rose Shimmer , Nike Flex 2017 RN SZ 9.5/ 898476-001 Black White Anthracite Women's Running ShoeSkechers Women's EZ Flex 3.0 Songful Slip-OnNike Womens Dunk low size 11 , NEW Womens Columbia Grand Canyon Outdry Running Hiking Trail Shoes Mud Cornstalk , ADIDAS WOMENS PERFORMANCE FRESH BOUNCE W FAMOUS RUNNING SHOES #S81806REEBOK CROSSFIT NANO 3.0 CF74 WOMEN'S ATHLETIC SHOES SIZE 7.5 PINK V53246 , Dawgs Golf Spirit Shoes - Womens Black/Soft Pink Size 10, 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."