14 DAY TRIAL // The Red Planet is full of natural phenomena that are somewhat bizarre, considering the fact that Mars' atmosphere is less than 1 percent as dense as Earth's. Mars lost its magnetosphere 4 billion years ago, so the solar wind interacts directly with the Martian ionosphere, keeping the atmosphere thinner than it would otherwise be by stripping away atoms from the outer layer.
Now, an instrument aboard NASA's Odyssey orbiter around Mars, called the Alpha Particle X-ray Spectrometer, recorded constant changes in the composition and movement of the Martian atmosphere. During summer, around 95% of it consists of carbon dioxide. Nitrogen accounts for almost 3% and argon for less than 2%.
When winter comes at one of the poles, it triggers massive changes in the atmospheric composition, because carbon dioxide freezes out of it to form a polar cap, causing a low-pressure system that moves air toward that pole.
"Argon stays in the atmosphere and becomes enhanced because it freezes at a much lower temperature," said Thanasis Economou, Senior Scientist at Chicago's Enrico Fermi Institute, where the spectrometer has been developed.
Now, it started recording interesting data, showing that on the Mars south pole during the winter, the argon concentration is six times higher than during the warmer seasons. "The amount of argon that comes with the air mass stays in the atmosphere," Economou explained. "Carbon dioxide drops, so the ratio of argon to carbon dioxide is increasing constantly until the next season."
Near the end of the winter season, rising temperatures evaporate frozen carbon dioxide back into the atmosphere, causing a high-pressure system that pushes the air mass back toward the equator.
"The fact that we see a signal at all means there's a lot of mixing between the polar air and the air at the tropics," said Ray Pierrehumbert, the Louis Block Professor in Geophysical Sciences at the University of Chicago, specialized in the evolution of climate on Earth and Mars.
"It gives you a way of inferring aspects of the Martian circulation that you can't observe at all with any other instrument that's out there," he said.
What happened on Mars in its past, correlated with present phenomena, could accurately predict Earth's future climate, so anything that can shed light on our own future is extremely valuable to scientists wanting to know more about our planet's fate.