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.Clarks Artisan Shoes 5.5 Women Dark Brown Pebbled Leather Slip On Loafer 1" Heel , womens pink ballet flats shoes size 7Steve Madden Multi-Colored Ballet Flats Shoes Size 8 , LOAFERS BROGUES LOW HEEL SHOES WOMENS LADIES SCHOOL FORMAL PUMPS TWO TONE SIZE , Clarks Artisan Ballet Flats Black Leather 6 M Loafers Active Air 87360 ShoesCrocs Iconic Comfort Blue Slip On Women's Shoes Size 10 AL4284Steve Madden Women's Lynn Sneaker, Mauve, Size 9.0 FOuu , New **ANTONIO MELANI** Kelsee Leather Peep Toe Wedge, 1" Heel, 7.5 MNew Talbots Quin Size 5.5 Red Crocodile Embossed Leather Loafers Boat ShoesADRIENNE VITTADINI Footwear Women's Angela Ballet Flat Black Size 7.0 , B35 Opal Slip On Loafer Flats, Denim, 7.5 US DisplayWomens Salvatore Ferragamo Sport Black Canvas Loafers Square Toe Size 8 B SQ8 , Dirty Laundry Jiana Slip On Sneakers 138, Vintage Rose, 9.5 US / 40.5 EUMadden Girl Women's stepp Fashion Sneaker , New Balance 530 Encap Sz 9 Womens Sneakers Multicolored , NIKE CORE MOTION TR 2 WOMEN'S TRAINING SHOE, WHITE, 9.5LADIES SHOES/FOOTWEAR - No Shoes Kid flat shoe redWomen's Ballerina Slipper Pumps Textile Grey NEWAnne Klein Harmonie Navy Reptile Womens Slip-On Size 7.5MSkechers? ~ SHAPE-UPS Strength Fitness Shoes ~ 11800 ~ Women Sz 8 ~ GOOD , Women's Asics Gel Kayano 20 Running Shoes 6 Black Teal Blue Purple Yellow T3N7NJosef Seibel Bronze White Leather Mary Jane Fashion Sneaker Women's 7-7.5 / 38NIKE REVOLUTION 3 LOW SNEAKERS WOMEN SHOES WOLF GREY 819303-009 SIZE 10 NEWWomen's Under Armour Speed Swift Swift II FW17 Size 7 New SMS Sample Blue , New Balance Roshe Two SI Oatmeal/Ivory. Size 8. Originally $130Nike WMNS Classic Cortez ALC PREM Terra Blush White AH5206-200 Women's 7.5 NEW , Skechers 11949 NEW D'Lites Play On Memory Foam Training Sneakers Women's US 7JARLIF Women's Platform Wedges Tennis Walking Sneakers Comfortable Lightweigh... , Sandro Albatorock Sneakers - Size 40Women Athletic Sports Sneakers Outdoor Running Jogging Navy Shoes 1704 a_C ,
"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."