‘Global’ Martian dust storm yields hazy pictures from the Curiosity rover
Image credit: nasa
Photos of a vast Martian dust cloud that would cover an area the size of North America and Russia combined have been sent back to Earth from Nasa’s Curiosity Rover.
The storm of tiny dust particles has engulfed much of Mars over the last two weeks and prompted Nasa’s Opportunity rover to suspend science operations.
In the last few weeks Opportunity has ceased contact with Nasa as the dust cloud is preventing sunlight from reaching its solar panels and charging the device.
However, the Curiosity rover (pictured in the dust storm) on the other side of the planet is nuclear powered and not subject to these solar limitations.
It is expected to remain largely unaffected by the dust and has been beaming back some impressive pictures from the surface of Mars while going through the extreme weather event.
Nasa said the Martian dust storm has grown in size and is now officially a “global” dust event.
Though Curiosity is on the other side of Mars from Opportunity, dust has steadily increased over it, more than doubling over the weekend. The atmospheric haze blocking sunlight - called “tau” - is now above 8.0 at Gale Crater—the highest tau the mission has ever recorded.
Tau was last measured near 11 over Opportunity, thick enough that accurate measurements are no longer possible for Mars’ oldest active rover.
Nasa is now trying to figure out the cause of the huge dust storms and why this one is still raging three weeks after it was first detected.
“We don’t have any good idea,” said Scott D. Guzewich, an atmospheric scientist leading Curiosity’s dust storm investigation.
Curiosity, he points out, plus a fleet of spacecraft in the orbit of Mars, will allow scientists for the first time to collect a wealth of dust information both from the surface and from space. The last storm of global magnitude that enveloped Mars was in 2007, five years before Curiosity landed there.
In the animation, Curiosity is facing the crater rim, about 30km away from where it stands inside the crater. Daily photos captured by its mast camera show the sky getting hazier. This sun-obstructing wall of haze is about six to eight times thicker than normal for this time of season.
Curiosity’s engineers have studied the potential for the growing dust storm to affect the rover’s instruments and say that it poses little risk.
The largest impact is to the rover’s cameras, which require extra exposure time due to the low lighting. The rover already routinely points its ‘Mastcam’ down at the ground after each use to reduce the amount of dust blowing at its optics.
Martian dust storms are common, especially during southern hemisphere spring and summer, when the planet is closest to the Sun. As the atmosphere warms, winds generated by larger contrasts in surface temperature at different locations mobilise dust particles the size of individual talcum powder grains.
Carbon dioxide frozen on the winter polar cap evaporates, thickening the atmosphere and increasing the surface pressure. This enhances the process by helping suspend the dust particles in the air. In some cases, the dust clouds reach up to 60km or more in elevation.
Though they are common, Martian dust storms typically stay contained to a local area. By contrast, the current storm, if it were happening on Earth, is bigger than North America and Russia combined, said Guzewich.
While dust storms occur on Earth in desert regions, conditions here prevent them from spreading globally. These include the structure of our thicker atmosphere and stronger gravity that helps settle dust. Earth also has vegetation cover on land that binds the soil with its roots and helps block the wind and rain that wash the particles out of the atmosphere.