Re: "This is fantastic news ... FOR SCIENCE!!!"
I think they were thinking in terms of the comet impacting Earth, which is, of course, even more unlikely (as near impossible as makes no difference) , as Rosetta just doesn't have the mass to significantly alter the comet's trajectory. And IMo you;re being unduly pessimistic - I wouldn't give Rosetta any effective chance at all from impacting Earth following its impacting the comet.
