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.Natural Soul by Naturalizer Brown Shoes 8 M Leather Slip On Loafers WomensMaypol Women's Espadrilles Anthropologie 36US 5/5 1/2 Turquoise Blue Suede , SC35 Blidge Dress Ballet Flats, White , Birko PremiumBirkenstock Boston Brown Suede Mule Clogs Solid Footprint 38 L 7 , Womens 7.5/38.5 BORN BOC Brown Leather Stitched Slip-on Hand Crafted Loafers , NEW WOMENS ANDIAMO PURPLE CASSIE SHOES SIZE 8.5W 8.5 W , ANTONIO BOSSI Diana Loafers Driving Shoes -Women's US 8 *Made in Italy , Crocs crocs Womens Citilane Flat- Pick SZ/Color. , FINN COMFORT Black Patent Leather Adjustable Shoes Womens Size 4.5 US 2 UK Exc. , TUK ANARCHIC Black Leather Brogue Mary Jane wingtip style Shoes Women's Size 7SPERRY WOMENS CREST VIBE LINEN LIGHT PURPLE SIZE 7 , Everlast? Sport Women's Andi black Athletic Shoe Color:black,Shoe Size:6,M newSkechers Men's Go Walk Performance 54141 Sport Walking Shoes [151C] , j crew blue rain flats bow size 6Mia Zoe Bow Faux Leather Slip On Sneakers, Women's Size 6M, Black , Skechers Shape Ups Size 8.5 Blue & Silver 11809 Womens Toning Walking ShoesRoxy Women's Minnow Sneaker,, Grey, Size 8.5 ArMA , Mint Asics S651N GEL Fit Nova Women's Running Shoes Size 11.5 Eu 44NIKE Training FLEX TR2 Womens Size 6.5 Athletic Running Shoes 511332-601 , Women's Blue Chuck Taylor Hightops, Size 7.5Call It Spring Women's Adauni Fashion Sneaker, White, 5 B USNIKE Air Womens Sneakers White Pink Size 11 Low Basketball Shoe 311157-161WOMENS DC CHELSEA SE SKATEBOARDING SHOES PEACH PARFAIT (PPF)Skechers Sport Women's Microburst One up Fashion Sneaker,Black,9 M USVANS New Authentic Marvel Vault Classic Lady Shoes Size USA 7Kenneth Cole New York Women's Kam Fashion Sneaker, Navy Floral, 7 M US , Nike Air Max Thea Jcrd W , HOKA ONE ONE Women's ROCKET MD Track Running shoe Cyan / White Shoes Training , NEW Nike FREE TR FIT 4 PRT sz 10 HYPER PUNCH RED Run Running Shoes Sneakers , New Adidas "ADIZERO XT BOOST" Women's Running Shoes Size 7 Blue/Pink S74412
"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."