On Nov. 10 the Mars Reconnaissance Orbiter, using its Mars Color Imager instrument, observed a dust storm forming in the Utopia Planitia region. The storm quickly grew to a size of about 10.4 km², ultimately moving into the southern hemisphere reaching as far south as Promethei before weakening and becoming confined the the Hellas Basin in the southern hemisphere.
Neither of the two rovers on Mars, Opportunity and Curiosity, had their operations disrupted by the storm. However, both were able to make some observations of the effects of the storm. The REMS instrument on Curiosity noted increased nighttime temperatures, and Curiosity’s and Opportunity’s cameras noted increased atmospheric opacity.
This is the first time since the Viking landers and orbiters were operating that scientists have had weather stations on the surface and in orbit while major dust storms formed.
Dust storms come seasonally on Mars, like hurricanes in the Atlantic basin. The storms are driven by carbon dioxide sublimating from the southern polar ice cap as spring comes to the southern hemisphere. Simultaneously, temperatures are dropping in the northern hemisphere, and the carbon dioxide atmosphere begins to freeze onto the ground. This creates pressure differences which can drive atmospheric disturbances, which have high winds and can pick up dust. In the past, these kinds of dust storms have sometimes grown to cover the entire planet. This was the case in 1971 when Mariner 9 reached the planet, and more recently in 2001 when the Hubble Space Telescope observed a storm in the Hellas Basin that grew to encircle the planet.
But this most recent major storm failed to grow that large. Now it is dissipating and confined to the Hellas Basin, a massive impact feature in southern Mars.
Malin Space Systems issues a weekly report on Martian weather that can be found here, along with an archive of weather reports going back to November 2007.
Malin’s latest report confirms that the large storm has mostly dissipated, and a few local storms have erupted around the edge of the southern polar ice cap.