Pope Benedict 16 did not endorse this view at all, nor did the
Vatican. A Vatican astronomer who is also a priest was interviewed
by a magazine and supported the idea of alien life as not being
incompatible with the teachings of the Church. It was his view,
not an official endorsement.
Presumably he would not have said such a thing if the Church
had a problem with this idea, especially in the current climate,
so that is good news for opening the masses up to ideas
beyond their narrow daily lives.