How Maven dodged a martian moon

When Nasa realised its spacecraft was on a near-collision course with Phobos, it was time for its first avoidance manoeuvre

Nasa successfully avoided a possible collision between its Maven spacecraft and the martian moon Phobos this week. The danger was spotted in late February by mission controllers at Nasa's Jet Propulsion Laboratory (JPL) in Pasadena, California.

Maven studies Mars's upper atmosphere and has been at the planet for two years. It follows an elliptical orbit that crosses the paths of Phobos and several other Mars spacecraft. This means that controllers are always on the look out for possible collisions.