what would happen if a Mars Bar hit the earth at 10,000 miles per hour?

10,000 mph = 4.5 km/s

If it falls from space at that speed, this is a rather slow speed.

However, it would probably melt while traversing the atmosphere (friction with air). At that slow speed, the friction might be insufficient to burn it up completely. Also, the air would probably succeed in slowing it down to its terminal speed in the troposphere (a speed of around 150 mph = 0.067 km/s).

At that speed, the melted content of the package would have time to re-solidify, giving a confused bar of... something (the original layered texture might be lost). This object would be arriving too slow to create much of an impact (although you might disagree if you get it on the side of the head).

It would have hit terminal velocity before it reached 10,000 miles per hour.

What have you done? I knew that buying you the Sadam Hussein Chemistry Set was a mistake but would Uncle Ahmedinijad listen? Oh No!

Easy. You'd be at the place where it would land and....open your mouth wide to try and eat it, irrespective of the fact that it would give your throat a fourth degree burn(wonder if there is such a thing).

A Mars a day helps you work, rest and splaaaaaaat!

The cad would bury itself in the ground. Or nestle itself in a round tree

It would more than likely melt before it got anywhere near earth.

It would create a Milky Way bar lol

We would fill a big gap till lunch time

It prove once and for all that there is life on other planets ........ and they eat candy bars.