UK astronaut Tim Peake is back on Earth after a historic six-month stay on the International Space Station.

The Earth gets a small companion. NASA scientists discover a small asteroid in an orbit around the Sun that keeps it as a constant companion of Earth and it will remain so for centuries to come.

NASA, the US space agency, together with Lima's International Potato Center (CIP) is conducting the pioneering experiment to determine whether potatoes are fit to grow on Mars.

An orbiting Nasa satellite has spotted an ancient, dried-up river on Mars - with the sort of branching tributaries we see in rivers on Earth.