TEHRAN (Press Shia Agency) – A giant dust storm has enveloped the entire planet of Mars, with dust clouds reaching up to 40 miles high, NASA announced Wednesday.

The dust storm has silenced NASA's solar-powered rover Opportunity since last week, by obscuring the sun. The robot rover has gone to sleep because its solar panels are unable to provide or recharge its batteries.

But NASA's other Martian rover, Curiosity, is nuclear powered and is mostly unaffected by the dust storm.

For NASA's scientists, Curiosity can offer an unprecedented chance to answer why some Martian dust storms last for months and grow massive, while others are small and last only a week.

"We don't have any good idea," said NASA atmospheric scientist Scott Guzewich at the Goddard Space Flight Center.

The dust storm is the biggest on Mars since 2007.

Martian dust storms are common, especially during the planet's spring and summer, when it is closest to the sun. As the atmosphere warms, winds generated at different locations mobilize dust particles the size of talcum powder grains.

The storms typically stay contained to one area on the planet. Guzewich said the current storm would cover an area larger than North America and Russia combined.

Scientists have been tracking dust storms on Mars for more than a century, using telescopes and spacecraft orbiting the red planet. Sometimes the storms are so intense and kick up enough dust that they can be seen by telescopes on Earth.