An astronaut on a spacewalk was forced to return to the International Space Station after mission control decided his jetpack was not safe.
Joe Acaba was five hours into a six-hour maintenance operation on an exterior robotic camera, when Houston decided the handles on the safety unit had 'popped out' once too often.
The jetpack itself is a back-up safety measure, designed to be used should any or all of the astronaut's multiple 'tethers' work themselves loose.
There is no suggestion that this had happened, but mission control's prime concern was for the safety of their colleague.
Joe Acaba, a teacher-turned-spacewalker, had already accomplished most of the task at hand – the replacement of a blurry camera which will be used to monitor the arrival of a supply ship, due in a few weeks.
By the time his jetpack was deemed unusable, the new camera was in place and he was making adjustments to the robotic housing in which it sits.