Would they tell you if an asteroid was to hit earth?

IF an asteroid was approaching Earth shouldn't.we be informed....????....(in 2009,...March 5th to be exact)....we were told that an asteroid almost hit Earth...three days prior, and only...78,500km away... asteroid named "2009 DD45"....should we not try to find a way to counter this threat rather than spending all our resources going green?...or should I say going "CARBON??"