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.Women's Liz Claiborne Stadium Dark Brown Leather Loafers US Size 7 M , Skechers Brown Adjustable Hook Loop Mary Jane Comfort Shoes Size 11 , Rocket Dog Spotlight Solar Power Oil Slick Womens Flip Flops , SALOMON Womens Brown Slip On Contagrip Suede Shoes Hiking Size 7.5 , Laamei Ladies Chaussure Women Spring Autumn Shoes Woman Zapatos Mujer ( -25% ) , Kenneth Cole Reaction Women's SOLEY ROLLER 3 LE NEW In Box Size: 9.5 COLOR WHITE , Geox Respira Mary Janes-Women's sz 7 BlackAmerican Eagle Outfitters Shearling Suede Flats Shoes w/Bow Mint Green Sz 6 NEW , Aerosoles Women's "On Call" Black White Stitch Buckle Kitten Heels Size 7.5M USNIB REPORT DSW Lena Floral Rose Ballet Flat Slipper Summer Night Shoes black 7Merrell Ortholite Shoes Taupe Mary Jane Breeze Comfort Mesh Flats Womens Sz 7Womens pointed toe platform shoe oxford slip on sneakerTROTTERS Womens LANDRY Black Veg Leather Ballet Flat Wedge US 8 S , Ivanka Trump Elise Brown Womens Shoes Size 7.5 M Flats MSRP $120 , Dansko Womens Black Leather Slip On Shoes 41 US 9.5 , Asics Gel-Exalt 2 Women's Black/Aqua/Pink Glow Training Sneakers 5MNike Air Max Lebron James Soldier V Shoes 454149-105 Women's Size 7.5 , Womens COLUMBIA Rogue HydroTrainer Running Walking Shoes Sz US 7 (G2)NEW BALANCE 860 v5 Women's Running Shoes Purple Lime Crosstraining Size 7 BMERRELL BARRADO MINIMALIST SLIP ON BREATHABLE OUTDOOR SHOE WOMENS SZ 7 BLACK GUCMerrell Hiking Walking Sneaker Casual Shoe Select Cush 8.5 Women Leather BlackXMDR Women's Fashion Sneakers Breathable Mesh Casual Sport Shoes Comfortable ... , Dexter Womens 7.5W Classic Comfort Golf Shoes Cleats Fast Twist White Tan Brown , Nike Zoom Rival Waffle Womens Cool Grey/Black/Pure Platinum/Wolf Grey 04719002 , Asics Gel-Quantum 360 CM Athletic Shoes - Women's Size 8, Flash Coral/BlackNike Women's Roshe One Print Dp Garnet/Blk/Gym Red/Vry Brry Running Shoe , New Balance WL574NEN Neon Pack WMNS Black Red Casual Sneaker NIB , Dansko Poron Women's Athletic Shoe US 11 42 EUR , Keen Targhee II 1004089 Womens Hiking Trail Shoes Sneakers 9.5 , Womens Asics Phantom Gortex/Vibram Sz 9.5 ,
"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."