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 Main Man NEW Loafers Womens Slip On Shoes 7.5 B Black Leather , ISAAC MIZRAHI LIVE Women Casual Sneakers Size US 12 M, brown suede fabric , NEW~Women's Sam & Libby Bow Ballet Flats Black Silver Blue Metallic size 7.5 , White Mt. Womens casual Loafers Size 7MDansko Womens Eartha Suede Slip On Clog - Brown | US 9.5-10 , Nine West Anastagia Flat - Women's Size 6M GoldDANSKO CLOGS VEGAN GRAY FLEECE FLANNEL SIZE 7 / 37 COMFORT ORTHOPEDICLUCKY BRAND Abelle 2 Black Suede Driving Moccasins Loafers Shoes Size 7.5 EUC , Clarks Sillian Bella Mary Jane Women size 8 BlackLuxury Rebel Womens Sari Silver Ballet Flats Shoes 10 Medium (B,M) BHFO 0785 , Klogs Missy Womens Clogs Shoes Display Model Leather Mahogany 9.5 MAllagiulia Suede Moccasin Flat With Fringe And Tire Tread Sole , Kenneth Cole Womens Studded Black Flats 6 MSaucony ProGrid Guide 6 Mesh Teal Running Shoes Women's 5M Light OverpronationNew Balance 101 Heather Grey Pink WL101HG Women's Casual Athletics Shoes 9 40.5Steve Madden Womens hachi Closed Toe Ballet Flats, Black leat, Size 11.0 AFlR , New Dolce Vita Womens Nate White Leather Fashion Sneaker Size 7.5 , NIKE FLEX TR 5 TRAINING RUNNING SHOES - MULTI COLOR ( SIZE 8 ) WOMEN'S77% off NEW JOSEF SEIBEL Fallon Shiny Velour Sangria Comfort Shoe sz 5 ret $135 , Skull Fashion Women Running Trainers Walking Shock Absorbing Sport Shoes Sneaker , Brooks 7 White Leather Sneakers Walking Running Shoes Women's Size 9Everlast Womens Sz 8 Athletic Shoes Pink Slip On Walking Mesh Memory Foam SportSuperga Navy Blue Cotu Classic Sneakers Womens Size 10 Mens 8.5Merrell MQM Flex Hiking Shoes (For Women) Size 8.5OLUKAI SAMPLE WOMENS NEW KIA'I TRAINER RUNNING TRAIL SHOES US7 , saucony mirage 3 running shoes size 9NIB WOMENS STEVE MADDEN LANCER BLUSH NEOPRENE SNEAKERS SHOES SZ 6-11 , BRAND NEW - New Balance Women's Running Course 8.5 US Pink and Black 750 v1Steve Madden Ellis Slip On Sneakers, Metal MultiNew Women's Puma Pink Kinder-Fit Shoes - Size 2 - NWT ($55)
"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."