
here's some interesting info though:
impact.arc.nasa.gov/intro_faq.cfm
As far as warning goes, the short answer is "we will either have a long lead time or none at all."
( , Sat 8 Dec 2012, 22:48, Reply)

thank goodness Jupiter has the habit of soaking so much of these cosmic pebbles heading our way
( , Sat 8 Dec 2012, 23:04, Reply)

That despite being thirty years old, I re-bought off abebooks.co.uk a few months ago
'The Science in Science Fiction' by Nicholls, wonderful read
( , Sun 9 Dec 2012, 0:01, Reply)