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.Aerosoles Women's Wish List Dark Brown Leather Slip-On Loafer 7.5M , Crocs Flats Black White Band sz 7 Womens Discontinued StyleWomen's SAS Kiltie Leather shoe/Loafers tan Made in USA size 9 Slim retail $137Cole Haan Country womens loafers shoes 6.5 B brown leather Low Heel Italy Made , SAS Tripad Comfort Slip On Loafer Women's Size 7 S Narrow -BurgundyWOMEN'S NATURALIZER GALITA MULTI COLOR LEATHER FLATS -NWOB - NEW CLASSIC SHOES!Born Black Leather Loafer Size 8.5/40 M/W Slip On Comfort Shoe W32448 , Marc Fisher Analia Pointed Ballet Flats, BlackPried Justice Leather Flats - Womens Size 39(US8)Womens Wedge Heel Festival Fashion Platform Summer Casual Chic TrainersAdam Tucker Womens Nikki Leather Closed Toe Ballet Flats, Tanljg, Size 8.0 iAGyLADIES / TEENS DUCK HEAD BLACK CLOGS SIZE 7 1/2 MADE IN BRAZIL, FREE SHIPPING , Reebok Runtone Size 8.5 Women No Insoles Cleaned , Saucony Womens - Green Running Shoes Size 8 (326431)Fila Women's 9 Memory Outreach Shoes Foam Athletic Gray Mint (E) , Land's End Womens Tennis Shoes Slip On Sz 6B Blue , Altra Repetition Zero Drop Running Shoes A2345-2 Black Pink Gray Womens sz 9.5BASKET en cuir victoria_65114 Anthracite Neuves , Womens Summer Casual Creeper Pumps Wedge Heel Breathable Slip On Sneakers Shoes , Nike Women's Air Max Thea 599409-300 (US 7.5) , Kenneth Cole New York Womens Kam Ballet Leather Closed Toe, Storm, Size 6.0Puma Women's Faas 550 NM Running Shoe - Vivid Blue/White (18629-04) , Nike Women's Flex Contact Running Shoes Black/White 8 , Hummel Unisex-Erwachsene Slimmer Stadil Ace Sneaker Black Size 5 , Reebok Size 6 REALFLEX SELECT Coral Pink Running Sneakers New Womens Shoes , Asics Gel Kinsei 6 Running Shoes Eight 1/2 8.5 Women's 40 European Gray & Blue , WOMEN'S PUMA CARSON 2 X KNIT PEACOAT-PUMA WHITE SHOES SIZE 7.5Vtg Nike Air Force I Unicorn Cotton Candy Mid Calf Boots Pink Blue US 7 (020103) , Converse Women Chuck Taylor All Star 132298F Rasberry Size us 10 NWOBASICS Womens Gel Kayano Running Shoes Green Yellow Size 9
"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."