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.CROFT & BARROW Leather Strappy Slides MULES Clogs Mary Janes WOMEN SHOES Sz 10 : , Womens Diamante Fashion Platform Sliders Slip On Mules Summer Shoe SandalSkechers Womens The Menace Top Cat Woven Slip On Fashion Loafers Shoes BHFO 5039Skechers Womens Bobs B-Loved Round Toe Loafers, Black, Size 6.0 T08RBeacon Womens Jeannie Suede Closed Toe Loafers Cobalt Size 7.5 , BARE TRAPS 'Jami' Size 10 M Tan Suede Leather Med Wedge Heel Slip-On LoafersNine West Juanita Mules Leather Woven Slip on Shoes NEW Tan Brown Women's 8.5Klogs Haley Display Model Shoes Distressed Leather Iron 6 M , NIB Anthropologie Chelsea Crew Velvet City Flats Sz 37 EU New Shoes Chelsea Crew , Klogs Missy Womens Clogs Display Model Shoes Red/Black Flower 8 MWomens Adidas Stan Smith sneakers, size 6 (Fits 7.5-8) , Women's Cream/Denim/Teal Chuck Taylor Hightops, Size 6 , VANS AUTHENTIC white/white lo canvas pro skate era shoes . women's 5.5 / kids 4Parrot Print Women Slip On Running Shoes Breathable Sports Casual Shoes Athletic , UNIONBAY Women's Shtng Str Fashion Sneaker, White, 9 M USSkechers Shape Ups Womens Size 8.5 Pink Black Gray Shoes ~ USED , Fila Women's White BBN 84 Retro Shoes Size 7.5 US , Women's CONVERSE Breakpoint B White Gold Trendy Athletic Shoes , Skechers Sport Women's Gratis Bungee Fashion SneakerBlack9 M US , Cardigan Welsh Corgi Print Slip Ons For Women- Express Shipping , Women's Dunk Low Black Metallic Gold sz 6.5Amazing Chihuahua Print Running Shoes For Women-Free ShippingNEW Adidas Women's Superstrap Slip-On Sneakers Size 8.5/WHITE (BY2885)Brooks Adrenaline GTS 18 Running Shoes, Women's Size 12-2E, Navy/MintNEW DIADORA B. ORIGINAL GREEN WHITE SNEAKERS SHOES TRAINERS WOMENS 6 MENS 4.5 , New Nike Womens Free Focus Flyknit 2 Training Shoes 880630-600 sz 7.5 PunchMountain Warehouse Womens Breathable Shoes Waterproof and Mesh Lining Size 6.5 , New Skechers Womens Slip-On Shoes Grey Comfort Walking 7.5 8.5Nike Women's Flex Fury 2 Black Hyper Pink Anthracite Sz 7 Pre- owned , MERRELL MARY JANES BROWN LEATHER LOAFERS SLIP ONS WALKING WORK SHOES WOMENS SZ 8
"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."