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.Sperry Womens Ballerina Flats Plaid Print Rope Braiding Size 7 , Juicy Couture Mara Women's C0024 Navy Ballet Flats Shoes Size 8.5 M , clarks shoes women 7.5 Slip Ons Ladies Metallic , Womens DKNY Slip On Shoes Size 8.5 Pink Gold Donna Karan , Dark Burgundy Brown CLARKS Unstructured Slip On Lined Perforated Low Shoes 8.5 M , Women’s Plaza Bandeau Espresso Merrell Moc Slingback Shoes Size 6HUSH PUPPIES NEW BLACK FAUX SUEDE WEDGE SHOES SIZE 8Klogs Natalie Women's Clog Shoes Display Model Denim Shimmer 6M, Euro 36 , Dolce Vita Women's Cooper Oxford, Charcoal Velvet, Size 6.0 , Dr. Scholl's Womens wander up Closed Toe Loafers, Black, Size 7.0 1q6j , Ecco Street Evo One Golf Oxford Women size 41/10-10.5 LeatherWomens Vogue Black Sneakers Pumps Slip on Shoes Running Athletic Wedge Ch8 newEarth Shoe Womens 6 Light brown Sybil9 chunky leather penny loafer 3979757 , Vans Off The Wall Women's Shoes Sz 8.5 M Mens 7.5 Burgundy Casual Comfort , NEW! RELAXED FIT: BREATHE EASY – MANTRA 23019 BLK 98M pmNike Shoes 6.0 Size 8. Green And White in Good ConditionNEW New Balance WXC900HR Women’s Team Sports Shoes with Cleats Size 10 BK-Swiss Women's New Haven Snake CMF-W Fashion Sneaker, Gold/Off White, Size 6.5Adidas Superstar Shoes; Women's Size 10NIKE AIR MAX THEA Fuchsia Pink Women’s SZ 9.5Women's STEVE MADDEN Beale Women Grey Exquisite (in) Workmanship Athletic Shoes , Women's air jordan 1 Quality And Quantity Assured Athletic ShoesSkechers 23317 Sport Womens Microburst Topnotch Fashion Sneaker , Onemix Running Shoes For Ladies Soft Insole Walking For Outdoor Trekking Sneaker , VANS SK8 HI SLIM OVERWASHED BLUE GRAPHITE MENS 3.5 NEW NIB WOMENS 5 SKATE SHOES , Womens NIKE Free 3.0 Running Blue Training Trainers 641649 004 , Guess Verna Pull-On Sneakers, Pewter Multi, 11 USStylish Sheep Curls Women Shoes Comfortable Platform RounToe Sports Loafer ShoesWomen's Merrell Satellite Moc slip on shoe pigskin water resistant NEW size 6 , JiYe Athletic Shoes Men's Women's Outdoor Tennis Jogging Walking Fashion
"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."