2001 Planet-Encircling Dust Storm

The 2001 global dust storm was the largest observed in the modern robotic era at the time of occurrence, and the first to be tracked continuously by an orbiting spacecraft (Mars Global Surveyor) from initiation through decay. It began as a regional storm in Hellas Basin before expanding planet-wide within two weeks. The storm's peak opacity made surface solar illumination comparable to a heavily overcast Earth day. Mars Odyssey's arrival during the storm's decay required mission planners to adjust its aerobraking profile, as the elevated dust had expanded the upper atmosphere.