http://rt.com/news/paint-asteroid-earth-nasa-767/
Looks like we are due for that comet that Arthur C Clark promised us in Rendezvous With Rama.
If it hits they are saying it will be like that one that hit Siberia early in the 20th century-not enough for extinction but very severe nonetheless.
If it misses us and the moon - what will it look like from the ground?
If it hits the moon-how deep in the smelly stuff are we?
Will civilians be able to predict where and when it will strike or do we have to take big brothers word?
I heard it was about 150 meters in diameter. That's about 500-1000 megatons. Depending on where it strikes, ocean or land (ocean has better odds statistically) it would be roughly as bad as "two Krakatoa" eruptions. The Tunguska blast in Siberia was about 5-10 Megatons, maybe as much as 30. So if this asteroid were to impact, it would be much worse. Also Tunguska was an airburst, it exploded before it could reach the ground.
Ocean impact would create large tsunamis, which in the right place, could kill up to 1-2 Billion folks if it hit "just right" in the Indian Ocean centered on India and the populous areas of SE Asia. Maybe 500 Million right away, the rest due to infrastructure collapse.
Worldwide, summers would fail for one or two years, be crappy, in the 50's or 60's max in the mid latitudes. Winters would be harsh. Then things would return to normal.
If it hit the moon, not much at all. The majority of the ejecta would not hit the Earth, and that that did, the majority of that would be of a size to burn up in the atmosphere. Just my WAG... but I think that a lunar impact would create just a statistical blip for a few years in the level of rocks that are hitting us all the time.
If it went by? Somewhere inside a sphere bound by the Moon's orbit as the diameter, centered on the Earth? It looks like a low magnatude star sliding on by, not too different than watching a dim satellite move across the sky. Even one that was a Dino-killer and several kilometers or miles in size would not be too different looking.
A comet, that would be SPECTACULAR. The coma of gas and dust would be bigger than the moon and fairly bright, assuming it was a relatively fresh and active nucleus that hadn't been evaporated/burned out by prior passes to the inner solar system and sun heating etc.
