Jets shoot out from comet Wild 2 in this composite image taken by the Stardust spacecraft from a distance of about 5 kilometres (Image: D Brownlee/NASA)
I have to wonder if we would recognize an extrasolar comet if we managed to sample one. I suppose that's one of the reasons we're looking at our own native comets.
What?! Now dirty snowball... Walt Thornhill was right.
http://www.thunderbolts.info/tpod/2006/arch06/060217deepimpact3.htm
http://www.thunderbolts.info/tpod/2006/arch06/060216deepimpact2.htm
http://www.thunderbolts.info/tpod/2006/arch06/060217deepimpact3.htm