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.Keen Black Leather Mary Jane's, 7.5M... GREAT Condition!MINNETONKA THUNDERBIRD WHITE SOFT SOLE WHITE MOCCASIN SIZE 7 , Sam Edelman Circus Womens Shoes QUEEN BEE 7.5 M Espadrille Canvas, New , Aerosoles Stitch N Turn slip on loafer shoes size 9.5 M faux croc , CLARKS Bendables Women's Burgundy Leather Slip On Mules Clogs Size 7Merrell Womens Walking Loafer Sz 8 Med Brown Taupe Mary Jane Comfort Casual Shoe , ROMIKA Ibiza 62 Sandal NIB Leather Flower Top Wedge Mule Slide Brown 38, 39 $120 , JAMBU Rosie Eco Mary Jane Biodegradable Flats Red Textile Shoes Womens Size 9M , Cole Haan Nke Air Womens Shoes Slip On Black Loafers Clogs Mules Size 8.5 BWomens Havaianas Slim Crystal Glamour Beach Lightweight Rubber Flip Flop US 6-11 , Jessica Simpson Womens Nessa Walking Shoe- Select SZ/Color. , Clarks Georgia Black Leather Wide E OR EE Fitting Slip On ShoesVasque Ion GTX Cross Trail Shoes Womens sz 6.5 Medium Wasabi Grey Hiking WalkingWOMEN'S PRADA BEIGE LEATHER LOAFERS/SHOES MADE IN ITALY SIZE 37 , NATURALIZER SOPHIE NICKEL ALLOY METALLIC LEATHER LOAFER WOMEN SHOE SIZE 8.5 M , les p'tites bombes ballerines 6-ELLA Argent P39 neuves Aut/Hiv 2018/2019 , Clarks Bendables Brown Leather Suede Mules Loafers Clogs Block Heel Boho Sz 9NIKE Womens Downshifter 7 White Running Training Athletic Shoes Size 10 F3-127Vision Street Wear Womens Suede Hi Retro Skate Shoes, Purple/White, US 7 , Easy Spirit Rustic Slip On Sport Sandals, Navy Multi, 6 USFENTY FENTY PUMA by Rihanna Hi Trainer Sneaker Size US 7.5 NIB $190Reebok Women's Print Smooth Clip Ultk Track Shoe 5.5 B(M) US - NEW IN BOXChinese Hamster Printed (Black/White) Running Shoes For Women-Free ShippingWomens ADIDAS SUPERSTAR W White Leather Trainers CG3354 , Saucony Women’s Ride 8 Pink Blue Running Shoes Trainers Size 8 Medium Used.VANS Classic Slip On (Velvet) Oxblood Black Skate Shoes Women's Size 5.5 , Vans Sk8 Hi Slim Camellia Rose Parisian Nights Women's 9.5 Men's 8 Skate Shoes , Woman's Aurora Medium/Wide Sneaker Boot Size 8M -Blue/Grey/ChiliPuma Roma Ladies Wedge Sneakers Grey/ Black/Pink Sport Lifestyle , Saucony Cohesion9 Sz 5.5 Gray Blue Sneakers Walking Running Work Shoes For Women
"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."