Mars' atmosphere might be thin but its climate is quite complex. NASA's Mars Orbiter has revealed a pattern of three large seasonal storms that take place one after the other each year, during the southern hemisphere spring and summer.
"Recognizing a pattern in the occurrence of regional dust storms is a step toward understanding the fundamental atmospheric properties controlling them," said David Kass of NASA's Jet Propulsion Laboratory, and lead author of the study, in a statement.
On Mars, the dust is strongly correlated with the temperature of the atmosphere. Dust absorbs sunlight more than clean air, so it will heat more. This temperature difference can reach more than 35°C (63°F). The heating generates planet-wide winds and the downward motion of warm air outside of the dusty regions can be observed from orbit.
"When we look at the temperature structure instead of the visible dust, we finally see some regularity in the large dust storms," Kass said. "We still have much to learn, but this gives us a valuable opening."
These findings were reported in a paper in the journal Geophysical Research Letters. NASA has been monitoring atmospheric temperatures on Mars since 1997, and these storms have appeared regularly for six recent Martian years (which are about twice as long as an Earth year).
Most of Mars’ storms are very localized, reaching 2,000 kilometers (1,200 miles) across at the most and dissipating in a few days. The ones being studied instead are much larger and they can cover up to one-third of the planet. Twice, since 1997, a storm has enveloped the entire planet.
Storms on Mars are not actually as dramatic as "The Martian" portrayed them, but they can still cause damage to the probes and robots we send to the Red Planet, so it is important to study them in detail.