In 1966, a thin layer of carbon dioxide (CO2) was detected in the atmosphere of Mars by the Mariner IV, a NASA fly-by spacecraft. Researchers from the California Institute of Technology (Caltech) theorised at the time that Co2 levels in the atmosphere vary depending on the seasonal changes of Mars.
The scientists believed that as one of the poles faced the Sun, the polar deposit of CO2 ice would melt, leading to more CO2 in the atmosphere.
This would ultimately alter the atmospheric pressure of Mars and have major implications for the Red Planet’s climate, which has a surface pressure of just 0.6 percent that of Earth’s.
Scientists Robert B Leighton and planetary scientist Bruce C Murray, believed at the time “ atmospheric pressure could swing from just one-quarter that of today’s Martian atmosphere to twice that of today over cycles of tens of thousands of years.”
Now, a new model run by current Caltech experts has proved the 54 year theory to be true, which supports the theory that Mars once had free-flowing water.
The team state that as the CO2 packed ice melted in the past, it allowed more surface pressure to build, which suited for a better environment on Mars.
In theory, the CO2 packed ice deposit should not be possible, because water ice is more thermally stable and darker than CO2 ice; CO2 ice, scientists long believed, would quickly destabilise if it was buried underneath water ice.
A statement from Caltech said: “The new model by Buhler and colleagues shows that the deposit could have evolved as a result of the combination of three factors.”
1) the changing obliquity (or tilt) of the planet’s rotation.
2) the difference in the way water ice and CO2 ice reflect sunlight.
3) the increase in atmospheric pressure that occurs when CO2 ice sublimes.
Peter Buhler of NASA’s JPL, which Caltech manages for NASA, said: “Usually, when you run a model, you don’t expect the results to match so closely to what you observe.
“But the thickness of the layers, as determined by the model, matches beautifully with radar measurements from orbiting satellites.
“Our determination of the history of Mars’s large pressure swings is fundamental to understanding the evolution of Mars’s climate, including the history of liquid water stability and habitability near Mars’s surface.”
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NASA is expected to launch another machine to Mars this year – the Mars 2020 Rover – as the space agency ups the search for evidence of past life on the Red Planet.
The machine will also explore the Red Planet as preparation for humanity’s arrival, which could happen in the next decade.
NASA said: “NASA’s latest mission to Mars — a mission that will receive a new name before launch — will be the latest rover to head to the Red Planet, but it’s not going alone.
“To aid it in its exploration, it’s carrying the first helicopter that will fly on another planet.”
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