Two tiny robots have landed safely on an asteroid after a Japanese spacecraft dropped them there on Friday. The scientists behind the historic mission expressed their delight as the rovers sent back the first images from the surface of the space rock Ryugu. Dubbed MINERVA-II1, the robotic explorers are the first of their kind to be successfully landed on an asteroid. The Japanese space agency JAXA announced that both units were operational after a period of silence between the unmanned spacecraft Hayabusa-2 depositing them and connection being established with the team on Earth. "I cannot find words to express how happy I am that we were able to realise mobile exploration on the surface of an asteroid," said Hayabusa-2 project manager Dr Yuichi Tsuda. The rovers will use the low gravity conditions on Ryugu to hop across the asteroid's surface, measuring temperatures and sending images back to Earth via Hayabusa-2. "I was so moved to see these small rovers successfully explore an asteroid surface because we could not achieve this at the time of Hayabusa, 13 years ago," said project mission manager Dr Makoto Yoshikawa. The small rovers are the first component of Hayabusa-2's mission to Ryugu. Next month the spacecraft will deploy an explosive device to blast a hole in the asteroid, allowing rock samples to be taken from its depths. Following that it will release a French-German landing vehicle known as the Mobile Asteroid Surface Scout (MASCOT) to explore the surface in greater detail.