https://phys.org/news/2018-06-nasa-encounters-storm-science.html

"This is the ideal storm for Mars science," said Jim Watzin, director of NASA's Mars Exploration Program at the agency's headquarters in Washington. "We have a historic number of spacecraft operating at the Red Planet. Each offers a unique look at how dust storms form and behave—knowledge that will be essential for future robotic and human missions."

Dust storms are a frequent feature on Mars, occurring in all seasons. Occasionally, they can balloon into regional storms in a matter of days, and sometimes even expand until they envelop the planet. These massive, planet-scaled storms are estimated to happen about once every three to four Mars years (six to eight Earth years); the last one was in 2007. They can last weeks, or even months at the longest.