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 Trust Fund Slip On Loafer, White Leather, 8 M US , � Life Stride Soft System Mary Jane Flats size 8.5 M Tan and Brown Leatherette , Suede like brown shoes with fur from Japan Sneaker Flat Ladys ACQUA CALDA 8EVAN PICONE Womens Heels Sz 6 M Black Leather Cap Toe PumpsTommy Hilfiger FRANK8 Flat Slip-On Mules 234, Medium Blue Suede, 7.5 USKeds Women's Navy Blue Canvas Slip On Fashion Shoes Size 9 US SUPER CUTE EUC , Daniel Green Cogs Mules. Brown Suede With Flower Trim. Womans Size US 9 M , Charles David Women Gray Suede Floral Embossed Slide On Open Back Mule Shoes 6.5 , SAS Tripad Comfort Women Size 8.5 W Brown Distressed Leather Sandals USA , Sperry Women's Gold Cup A/O Honeycomb navy Boat Shoes, Women's US 5, NEWWomens Fur Furry Leather Embrodiery Fashion Mules Slippers Shoes Oxfords Plus SZ , New Balance Running Shoes Womens Size 8 WT610BP3 5096 SHA3 , Merrell Moab Ventilator Low Waterproof Hiking Shoes, Women's 9.5, "Dusty Olive" , BCBG Generation Black Cage Leather Sandals with Cork Heels Size 7womens size 11 asics gel gt-2000 running walking , Converse Chuck Taylor Brown Suede Leather Hi-Top Size Mens 4 Womens 6 , Salomon Womens Sz US 7.5 Loafers Hiking Casual slip on Shoes Black Suede ( B2) , Dr Weil Womens Size 7.5 Rhythm Sneakers Walking Running Shoes AMS 1st Ray Flex , Nike Size 7.5 Black Sneakers New Womens Shoes , Ryka Women's Dynamic 2.5 Cross-Trainer Shoe , WOMEN'S ASICS GEL KAYANO 24 size 10 !WORN LESS THAN 20 MILES! RUNNING SHOES! , Skechers Shape Ups Womens Model 11800 White Athletic Shoes Sneakers Size US 8.5MNX15 Women's Elevator Shoes SPOTTY WHITE Height Increase 5cm by FedEx Fast Ship , Under Armour Women's Speed Swift 2 Black/Rhino Gray/White SZ 7 2874 Columbia Women's "Caldorado II Outdry" Black - Orange Sneaker Shoes Size 8.5 NIBPUMA WOMENS VIKKY FASHION SNEAKERS , $79 NEW - EASY SPIRIT Women's EXPLORERMAP Nubuck WALKING SHOES - 7Kenneth Cole New York Kinsley Fashion Sneakers 018, Indigo, 8.5 US / 39.5 EU , Womens VANS Authentic Shoes (Pool Vibes) African Violet (Purple) Size 7 NWT , Brooks Cascadia 11 Womens Size 8.5 Running Trail Purple Orange Blue Shoes ,
"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."