Nasa is sending a helicopter to Mars, in the first test of a heavier-than-air aircraft on another planet.
The Mars Helicopter will be bundled with the US space agency's Mars rover when it launches in 2020.
Its design team spent more than four years shrinking a working helicopter to "the size of a softball" and cutting its weight to 1.8kg (4lbs).
It is specifically designed to fly in the atmosphere of Mars, which is 100 times thinner than Earth's.
Nasa describes the helicopter as a "heavier-than-air" aircraft because the other type - sometimes called an aerostat - are balloons and blimps.
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