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.NEW J Slides NYC Womens Black Slip On Shoes Casual J/Slides Snake Print Size 8 , NEW $69 Womens Skechers Reggae Fest Indefinitely shoes, size 11 , Women's BORN Strappy Black Leather Loafers Clogs Size 6 1/2M , Dexflex DEXTER Women's Pink Leather Slingback Low Wedge Ballet Flats Size US 6 M , Ryka Sandals Womens 7 gray White Slip Ons Grotto sport new shoesTS shoes TAKING SHAPE sz 9 / 40 Addison Slides wide fit rose gold bling NIB! , Sperry Top-Sider Women's A/O Venice Boat Shoes Navy / White Size 8MSUBLIMES BALLERINES XAVIER DANAUD NEUVES !!!!!! , MOSSIMO SUPPLY CO RED AND WHITE SNEAKERS SIZE 8 NEWDANSKO WOMAN SHOES BLACK SUEDE MARY JANE /US 8 , Women's Sperry Top-Sider A/O 2-Eye Silver Sparkle Boat Shoe 7PEEP TOE SUEDE BOOTIE WOMEN ANSON-1-34 MISBEHAVE OLIVE , ASICS GEL CUMULUS 18 Womens 9.5 US 41.5 EUR Running Shoes Size Aqua Blue T6C8N , Womens Skechers Shoes Size 10 Shape Ups , Sketchers Shape-Ups Shoes Womens Slip On Strap Brown Walking Size 10Adidas Stan Smith originals Silver women shoes , 2017 new Women breathable running shoes outdoor female sports shoes casual shoes , Women's Nike-Jordan-SL-23-Running-sprinter-White-Fire-Sunset-313541-101-SZ-W-9-M-7.5 High Safety Athletic Shoes , Women's BareTraps Women's Kami Flat Durable Service FlatsNIB Adidas Pure Boost X TR US women's 10, black/heather grey, blue,purple , [366013-03] WOMEN'S PUMA MUSE ELEVATED WN'SNEW Beloved WOMENS HIGH TOPS SHOES BURGER US 6-12 CUSTOM MADE TO ORDER , Women's Authentic Nike LunarEpic Flyknit 2 Running Shoes Size 9.5WANTED SHOES, COLUMBUS FASHION SNEAKER, WOMENS, CORAL, US 9M, NEW WITHOUT BOX , NEW Saucony Xodus 6 Womens Hiking Trail Running Shoes 5.5 Blue/Grey MSRP$120 , New Balance Women Shoes Elite Edition 580 Capsule Considered Chaos WRT580HS 7.5 , Keds Womens Baseball Stitch Shoes 11 NewUnder Armour Women's UA Fuse FST Running Training Walking Shoes - Apollo Gray 9 , Asics Onisutka Tiger Green White Pink Orange Shoes Women's Size US 9 , Fly Flot Silvia Black/Beige/Tan Suede Adjustable Strap Slide Sandals Sz 9-11 ,
"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."