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A discarded part of the Apollo 11 spacecraft that helped return astronauts from the first visit to the lunar surface may still be in orbit around the moon, rather than having crash-landed as once thought.

On 20 July 1969, NASA astronauts Neil Armstrong and Buzz Aldrin made history as the first two humans to land on the moon. They left the surface a day later using the ascent stage of their Eagle lander, rendezvousing with astronaut Michael Collins in the command module in lunar orbit. The empty ascent stage was discarded, supposedly on an impact course with the lunar surface, as the astronauts made their way home.

James Meador, a space enthusiast from California, says that impact may not have happened. Running simulations of the predicted orbit of the ascent stage using NASA software, he found that it should still be orbiting the moon today, roughly at the same altitude 鈥� about 100 kilometres 鈥� that it was left in. The moon has no atmosphere, meaning there is nothing to provide friction to drag spacecraft into a lower orbit, unlike with Earth.

鈥淭he Eagle was abandoned in lunar orbit, everyone just kind of forgot about it, and the assumption was it struck the moon decades ago,鈥� he says. But Meador鈥檚 simulations show its orbit might still be mostly stable today, travelling round the moon every 2 hours. 鈥淚t鈥檚 sort of wobbly,鈥� he says. 鈥淚t鈥檚 more or less where it was 52 years ago.鈥�

If the spacecraft, which is about 4 metres across, is in orbit, it could be detectable by radar from Earth. The massive Arecibo radio telescope would have been able to do this before its destruction last year, but other large radar facilities are available. 鈥淚t would be great to allocate a few hours of radar time and look [for it],鈥� says Meador.

The other Apollo spacecraft that visited the moon are unlikely to still be in orbit, as most of the ascent stages were purposefully impacted into the moon to produce seismic waves for seismometers left on the surface by the astronauts. It is unclear if the Apollo 11 craft is still intact, as fuel leaks may have caused it to disintegrate, but if it is, it could make for an intriguing find.

鈥淎 lot of people would be really excited to hear this thing still existed,鈥� says Meador. 鈥淚t would be amazing to bring it back to Earth and put it in a museum.鈥�