Moreover, many asteroids are chunky masses of rock and dust loosely held together by very little gravity, like loosely packed peanut clusters.

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Even if the delicate digital hardware running these machines keeps going, and even if they are the smartest roving robots this side of Mars, navigating through the scrub, dust and rock of the Mojave desert represents a complex challenge.

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If a rock has a coating of dust, hundreds of repeated pulses from the laser can remove those layers.

WSJ: Curiosity, the New Mars Rover | Visualizer

In 1994, as the Mandela government came to power, Motsepe left the law firm and struck out on his own, hoping to build a business contracting low-level labor like sweeping, where workers use brooms to glean gold dust from the rock surface after industrial mining crews have done their work.

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The rock is formed out of coagulated dust.

ECONOMIST: Planetary formation

Nasa's Mars rover Curiosity has used its brush tool for the first time to sweep dust off the surface of a rock.

BBC: Curiosity Mars rover deploys its rock brush

There's an important distinction between these two types of objects: Comets are mostly water, ice and dust, while asteroids are mostly rock or metal.

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Brushing away the dust gives the robot's survey instruments a clearer view of the texture and chemistry of the underlying rock.

BBC: Curiosity Mars rover deploys its rock brush