One of the main ion engines aboard Japan’s Hayabusa spacecraft shut down Nov. 4, raising questions about whether the asteroid sample-return mission will make it back to Earth by June 2010 as planned.

The Japan Aerospace Exploration Agency (JAXA) reported Nov. 9 that the Hayabusa project team had been unable to restart the engine despite five days of effort. Officials continue to investigate the problem and are working on an alternative plan for getting the spacecraft back to Earth.

Hayabusa was launched in May 2003 to retrieve samples from a small near-Earth asteroid called 25143 Itokawa.

The spacecraft failed in its November 2005 attempt to land on the surface of the asteroid and collect samples, but project officials believe it likely that some dust swirled into Hayabusa’s sample chamber during the attempted touchdown.