While the lack of sunlight doesn't keep the Curiosity rover from functioning, since the robot runs on a nuclear-powered battery, the Opportunity rover is powered by solar panels and is no longer receiving energy, which led to its recent shutdown. Curiosity is running on nuclear power, so it is not affected by the dust storm. In addition to Curiosity's weather observations on the surface, NASA has several other spacecraft tracking the storm from orbit: the Mars Reconnaissance Orbiter, Mars Odyssey and MAVEN orbiter studying the Martian atmosphere. They do know that dust storms are common, especially when Mars is closest to the sun during spring and summer. By the first week it took the size of North America, then "quickly doubled in size", and eventually continued growing.
Dust storms on Mars are actually quite commonplace. Curiosity has taken one of its trademark selfies (seen above) to show how the storm limits visibility, and that was on June 15th when the tau was half of what it is now. Curiosity was far away from the dust storm when it began, but now it's fully engulfed as the storm expands to cover most of Mars. NASA and its global partners - Europe and India - have the largest fleet of spacecraft at Mars in history, enabling the collection of a wide array of measurements.
For the past 14 years, Dr. Crumpler has been working with the Opportunity rover, making new discoveries and even naming parts of Mars after New Mexican areas.
The last storm of global magnitude to hit Mars was in 2007, five years before the Curiosity landed.
This animation, pieced together from pictures taken by Curiosity's Mast Camera, shows the weather darkening over Mars.
"Martian haze, all around". Opportunity is experiencing 11 Tau, a high enough value to make any accurate measurements from its instruments impossible. "One of the biggest: Why do some Martian dust storms last for months and grow massive, while others stay small and last only a week?"
New photos from Curiosity show a wall of haze over Gale Crater that is up to eight times thicker than normal for this time on Mars, NASA officials said. "The largest impact is to the rover's cameras, which require extra exposure time due to the low lighting".
Scientists first detected the dust storm May 30, and they do not know when it will abate.
"We don't have any good idea", said Scott D. Guzewich, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, leading Curiosity's dust storm investigation.
The dust clouds can reach 40 miles or more in elevation, which helps the suspended dust particles circulate and cause a global dust event.