Please check out the article in the BBC news website. It says that it is possible that the aliens, should they exist, may be without original sin.

Here's the BBC link:
http://news.bbc.co.uk/2/hi/europe/7399661.stm

Right, I didn't see that. This is more like an interview than an announcement. It seems to me that he's speaking more as a knowledgeable Church official rather than giving out new guidance.

He's speculating on things that he hasn't been told he can't speculate on and using his Catholic beliefs as a base.

Adam and Eve committed Original Sin. So their decedents have Original Sin (except for Mary). No alien Adam? God created them separately from humans; they may not have Original Sin.

Catholics have a long tradition of this sort of quirky "reasoning". They start with premises from revealed or observed "truth" and then proceed through deductive reasoning. When they come to a point where the reasoning would take them to a place that contradicts a Church teaching, they jump to the Church teaching and continue. It's jarring, and sometimes really weird. If I had to choose though, I'd take that over the outright hatred and outright rejection of reason that many other religionists teach.