China’s first planetary defence mission appears to be far more ambitious than Nasa’s Double Asteroid Redirection Test (Dart), according to a new paper outlining its plan to slam a spacecraft into an asteroid before 2030.Unlike Dart, a proof-of-concept that nudged one asteroid’s orbit around another, China is aiming for a more realistic planetary-defence test.It aims to directly alter an asteroid’s orbit relative to Earth, “or even break up its structure”, according to a team led by Li Mingtao,...