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 Ivyfish 2-Eye Glove Leather Boat Deck Oxfords Shoes Size 7Cute Bumble Bee Striped Ballet Slip On Slippers Flats Shoes Adult WomenCLARKS: EUC-"STRUCTURED" LOW HEELS-RICH CHERRY SHADE LEATHER-PLEATED-6.5 MEDIUM , Women's Dr Scholls Really Black Pointed Toe Comfort Ballet Flats Size 6.5 M , Women's Clarks Black Leather Slip-on Loafers Shoes Size 9 W , Sperry Bahama Silvery White Shimmer Top Siders - Size 5.5Womens Melissa Vivienne Westwood Ultragirl Shoes Size 10 , SAS EASIER Leather Women Shoes Comfort Burgundy 8.5 Loafer Slip On Antique Wine , Helly Hansen HHS161004W Women's Steel Toe Grey/Teal Sneaker 9MNew Balance Training 577 V3 Dark Gry/Hot Pnk WX577KM3 Womens Size 7.5B , MBT Lami Red Mesh Rocker Mary Jane Walking Sneakers Size 6.5 - 400092-06 , Tretorn Nylite Plus Sneakers - Women's Size 8.5, White , ASICS GEL-SONOMA 3 WOMENS Running Shoe Sz 11 NEARLY NEW , Puma Asha Alt 2 Womens Black Casual Sport Athletic Slip On Flat Shoes Size 11 , WOMENS REEBOK CL LEATHER SHMR in colors METEORITE / WHITE / ROSE GOLD SIZE 6.5Skechers Performance Women's Go Step Shift Walking Shoe , Asics Patriot 8 Womens T669N-1901 Rouge Red Running Training Shoes Size 8.5Merrell Womens Siren Sport GTX Waterproof Athletic Trail Hiking Shoes Size 10.5 , Skechers Street Women's Utopia - Gold Wing It - Fashion Sneaker - Size 7 - NewSkechers Women’s Air Cooled Memory Foam Lightweight Black Knit Mesh Shoes Sz.7.5Saucony Womens Kineta Relay Denim Sneaker- Select SZ/Color. , Women's Adidas Adizero Boston 6 Nobel Indigo Running Shoes Size 7 M AQ5992Balance Women's Fresh Foam Crush v1 Cross Trainer, Dusted Peach/Sunrise Glo, 5 B , Merrell Mesh Performance Siren Edge Hiker Shoes Blue Pink 6.5 NIB 40% OFF NIBASICS T7G6N-9790 WOMEN'S GEL VENTURE 6, GREY/PINK ALL TERRIAN SHOE NWB 65% OFFPUMA Roma White Black Sneakers Womens 7.5 Leather Upper Athletic Tennis ShoesVANS ISO 1.5 (Moroccan Geo) Classic White UltraCush Trainer WOMEN'S 7Nine West Gofish Womens Plaid Mid-Calf Winter Boots size 7.5Steve Madden Cash Womens Black Star Leather Sneaker New With Box Size 6 Eur 36 , Adidas Neo Women's Courtset Women's Suede Skateboard Shoes Navy Size 6.5 8 NIB ,
"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."