Question: what are the chances that an meteor will go through the earth's atmosphere and possibly hit earth?

Alan Fitzsimmons answered on 11 Mar 2014:

If the object is smaller than 50 metres across, it has almost no chance of getting through the atmosphere in one piece. Most of it will vaporise due to the intense heat, caused by friction with the air. But small bits of rock may break off at high altitude. These can fall to Earth as meteorites, which we can then pick up. this is what happened to the 20-metre asteroid that hit us in Russia last year.

If the object is between 50 metres and 140 metres across, it might make it through. It depends on what the object is made of, how it is put together, how fast it is travelling, and what angle it comes in at. So we think the rocky asteroid that hit Russia in 1908 was about 50 metres across, but didn’t quite make it through. An asteroid made of iron about the same size hit the USA 49,000 years ago, and made a crater a mile wide.

If the asteroid is large than about 140 metres across, it will probably hit the ground no matter what it is made of. Luckily things something size will hit us only once every 30,000 years, so it’s pretty rare.