NASA’s Mars Reconnaissance Orbiter observed a high number of ‘dust towers’ — concentrated clouds of dust that warm in sunlight and rise high into the air — during the global Martian dust storm in 2018.

Very dusty air heated by the Sun in the Martian atmosphere can power dust clouds that tower many tens of miles.

These clouds are most common in Mars’ rare and impressive planet-encircling dust storms, when dust is rapidly lifted from the surface and the planet’s atmosphere fills with a thick haze of dust.

“A tower starts at the Martian surface as an area of rapidly lifted dust about as wide as the state of Rhode Island,” explained Hampton University’s Dr. Nicholas Heavens and colleagues.

“By the time a tower reaches a height of 50 miles (80 km), as seen during the 2018 global dust storm, it may be as wide as Nevada.”

“As the tower decays, it can form a layer of dust 35 miles (56 km) above the surface that can be wider than the continental United States.”

Dust towers appear throughout the Martian year, but the Mars Climate Sounder instrument on board NASA’s Mars Reconnaissance Orbiter observed something different during the 2018 global dust storm.

“Normally the dust would fall down in a day or so. But during a global storm, dust towers are renewed continuously for weeks. In some cases, multiple towers were seen for as long as 3.5 weeks,” Dr. Heavens said.

The rate of dust activity surprised the team, but especially intriguing was the possibility that dust towers act as ‘space elevators’ for other material, transporting them through the atmosphere.

“When airborne dust heats up, it creates updrafts that carry gases along with it, including the small quantity of water vapor sometimes seen as wispy clouds on Mars,” the researchers said.

They previously showed that during the 2007 global dust storm, water molecules were lofted into the upper Martian atmosphere, where solar radiation could break them down into particles that escape into space. That might be a clue to how Mars lost its lakes and rivers over billions of years, becoming the freezing desert it is today.

“Global dust storms are really unusual. We really don’t have anything like this on the Earth, where the entire planet’s weather changes for several months,” said Mars Climate Sounder scientist Dr. David Kass, from NASA’s Jet Propulsion Laboratory.

With time and more data, the team hopes to better understand the dust towers created within global storms and what role they may play in removing water from the Martian atmosphere.

The findings appear in two papers in the Journal of Geophysical Research: Planets and the Journal of the Atmospheric Sciences.

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Nicholas G. Heavens et al. Dusty Deep Convection in the Mars Year 34 Planet-Encircling Dust Event. Journal of Geophysical Research: Planets, published online November 11, 2019; doi: 10.1029/2019JE006110

Nicholas G. Heavens et al. An Observational Overview of Dusty Deep Convection in Martian Dust Storms. Journal of the Atmospheric Sciences, published online October 16, 2019; doi: 10.1175/JAS-D-19-0042.1