"It looks very scary, " Russian cosmonaut Oleg Kotov told reporters via a video link.

BBC: Dispersed oil caught in the Gulf of Mexico 18 May

"This is the time when we have to say goodbye to our friends, our colleagues, the excellent crew of shuttle Atlantis that did an excellent job performing three EVAs, installing the new Russian module, having good fun, enjoying living on the station and working in space, " the ISS Expedition 23 commander Oleg Kotov told Ken Ham, who leads the Atlantis crew.

BBC: Atlantis set for 'final' return