Side-by-side movies shows how dust has enveloped the Red Planet, courtesy of the Mars Color Imager (MARCI) camera onboard NASA’s Mars Reconnaissance Orbiter (MRO). The view from May shows Valles Marineris chasms (left), Meridiani center, an autumn dust storm in Acidalia (top) and the early spring south polar cap (bottom). The view from July shows the same regions, but most of the surface was obscured by the planet-encircling dust cloud and haze. NASA
We have dust storms here on Earth, and we’ve observed them on Mars, too. But occasionally something much more dramatic happens on Mars: Multiple dust storms grow and come together to cover the entire planet in a dusty haze.
Scientists are still learning about these massive global storms and what causes them, and now they have learned more about dust towers, an extreme phenomenon seen during the storms. These huge dust clouds are denser than normal clouds and also climb much higher into the atmosphere, forming dramatic columns which reach up into the Martian sky. They can reach up to 50 miles into the air and decay to form a layer of dust 35 miles above the surface which can be wider than the continental U.S.
Researchers think that these towers form when clouds of dust are warmed by sunlight and start to rise. Water molecules which are trapped inside the towers rise along with the dust, in a manner NASA describes as “like riding an elevator to space.” Normally, dust towers occur occasionally and might rise and fall within a few days. But during a global storm, the towers are much more common and can last for three weeks or more.
“Normally the dust would fall down in a day or so,” researcher Nicholas Heavens of Hampton University in Hampton, Virginia said in a statement. “But during a global storm, dust towers are renewed continuously for weeks.”
The researchers believe the dust tower phenomenon may even be responsible for Mars losing its water. Scientists know that billions of years ago, Mars had liquid water on its surface and could even have been a lush planet like Earth once. But this water was lost to space over time as Mars’s atmosphere thinned. The dust towers are one way in which water could have been taken away from the planet’s surface and into the atmosphere, where solar radiation can evaporate it into space.
To learn more about the dust towers, researchers need to see more global dust storms in action. But they are relatively rare events, with only about a dozen observed to date. “Global dust storms are really unusual,” Mars Climate Sounder scientist David Kass said in the same statement. “We really don’t have anything like this on the Earth, where the entire planet’s weather changes for several months.”
The findings are published in two papers in the journals JGR Planets and the Journal of the Atmospheric Sciences.