NASA says it has successfully completed its first test flight of a mini-helicopter that will explore Mars.
The US space agency is working on ambitious plans to fly the drone-type device in the skies above the Red Planet in 2021.
Until now, exploration on other planets had been restricted to rovers on the ground and NASA hopes the helicopter will reveal a new perspective on Mars' surface.
It will be a difficult technical feat, however, as the device will be controlled remotely from hundreds of millions of miles away and flown on top of Mars's thin atmosphere.
Temperatures on the planet drop as low as -90C (-130F) at night.
NASA tested the mini-helicopter, which weighs just 4lb (1.8kg), in a vacuum chamber at the space agency's jet propulsion laboratory in Pasadena, California.
The chamber swaps nitrogen, oxygen and other gases for carbon dioxide to mimic the atmosphere of the Red Planet.
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Test conductor Teddy Tzanetos said: "Getting our helicopter into an extremely thin atmosphere is only part of the challenge.
"To truly simulate flying on Mars we have to take away two-thirds of Earth's gravity, because Mars' gravity is that much weaker."