A SpaceX rocket upper stage is expected to crash unintentionally into the moon on Wednesday after it launched two lunar landers more than a year ago. Scientists and amateur observers are interested in the event because it offers a chance to study lunar debris impacts and underlines concerns about increasing amounts of space hardware and junk in orbit.

Tracker Bill Gray predicts the stage will strike near Einstein Crater at about 5,400mph, releasing energy comparable to three tonnes of TNT. The impact may create a crater about 27 metres wide and five metres deep; while its flash is unlikely to be visible from Earth, dust and debris could be observable through telescopes for several minutes. Nasa’s Lunar Reconnaissance Orbiter and South Korea’s Danuri orbiter are expected to photograph the site before and after impact.