The Mars Reconnaissance Orbiter has been tracking the storm using its Mars Color Imager since mid-November. The storm came within 837 miles of Opportunity, slightly lowering the atmospheric clarity above it. On the other side of the planet, Curiosity was able to detect atmospheric changes using its Rover Environmental monitoring Station (REMS). Decreased air pressure and a rise in overnight temperature were observed.
"This is now a regional dust storm," said Rich Zurek, chief mars scientist at NASA's Jet Propulsion Laboratory. "It has covered a fairly extensive region with its dust haze, and it is in a part of the planet where some regional storms in the past have grown into global dust hazes. For the first time since the Viking missions of the 1970s, we are studying a regional dust storm both from orbit and with a weather station on the surface."
Each year on Mars lasts around two Earth years, and the dust-storm season began a few weeks ago, coinciding with the start of spring in the southern hemisphere. Regional dust storms, like the one measured last week, expanded to global hazes in 2001 and 2007, but such large storms have not been detected since.
"One thing we want to learn is why do some Martian dust storms get to this size and stop growing, while others this size keep growing and go global," said Zurek.
(Image courtesy NASA/JPL-Caltech/MSSS)