how can we tell that objects from space have hit earth?

Question

and how do scientists work out if another impact is likely soon?

Answer 1

Craters, metorites have non-terrestrial isotopes.
Age of craters is determined giving an average time between large impacts.

Answer 2

It is usually easier to see these from a satelite image or aerial view. Just look at the Moon. That had a nice few hits, all craters. It is 1/4 the size of Earth. Earth had a nice few hits. The meteor impact in Arizona, giant hole... Hudson Bay looks like as if it is a circular shape and near the Alps may indicate that there was an impact there one time. There is evidence in the Carribean that there was a massive impact there over 65 million years ago, the soil content and examples taken from all over the world suggests that there was dust cover around the planet for many years.
Another impact is inevitable, but when is the question.

Answer 3

Impact craters and direct observation. People have seen meteorites streak through the sky or crash through their roofs.
Scientists are working on tracking some of the larger objects. They know the physics and math needed to calculate the path of an object. They are not 100% accurate, but they are getting better at it.

Answer 4

From the changes to the surface where they struck producing telltale heat/shockwaves, and by their chemical composition, which is not only different, but contains isotope ratios not found on Earth. And secondly, by computing the orbits of those thousands of heavenly bodies which are already known.

Answer 5

The damage and scars they have left behind. Crater Lake is one example.

Answer 6

By it's Molecular Carbon tracks...( Charged and In-Charged Matter ) To get the scoop on it first, you have to get the scope on it!

Answer 7

By the bloody big holes they have left!!

Answer 8

Our heads hurt.

Answer 9

really difficult to answer that question...