Japan lands tiny robots on far-off asteroid

Hayabusa2. Photo credit: Wikipedia/Go Miyazaki

Two small robotic rovers have landed on an asteroid currently 300 million kilometres away from Earth - about twice as far away as the sun.

They were released from Japanese spacecraft Hayabusa2, which left Earth in 2014 and arrived in orbit in June this year.

 The cylindrical rovers measures just 18cm across and will make small hops on the asteroid, named Ryugu.

"Each of the rovers is operating normally and has started surveying Ryugu’s surface," the Japan Aerospace Exploration Agency (JAXA) said in a statement.

Ryugu is about one kilometre across, and its low gravity will allow the rovers to jump up to 15m in the air to take measurements and take photographs.

Two more rovers are expected to be dropped before Hayabusa2 leaves Ryugu and returns to Earth.

Ryugu is classified as a potentially dangerous asteroid, but also a valuable one - an estimate of its value to mining firms is NZ$120 billion.

Ryugu's orbit brings it close to Earth on occasion, but it's currently on the other side of the sun.