Edit: It seems more Italian newspapers are reporting this quote than just this one site, but for an announcement of this importance, I'm still not going to believe it until we get some more confirmation.
Slate specializes in punditry rather than reportage, I wouldn't worry too much about it. If it's BS NASA will clarify or deny within a few hours, but there have been hints leaking from several sources about some exciting news that was still under embargo while they continue testing. I think it's OK to post since it includes a legit source/scientific forum.
"La Gazzetta del Mezzogiorno" is not a blog, it's a newspaper. The news was reported by other Italian newspapers too, quoting Charles Elachi's words during a speech held in Rome.
