How do meteorites form in space?

Meteorites come from many different sources. The fact that many are made of iron/nickel, 'stony' or 'carbonaceous' means that there were parent bodies that had evolved to become chemically differentiated prior to being smashed into the smaller fragments. There are several unique families of meteoritic material suggesting at least as many larger parent bodies several miles across up to hundreds of miles across. Inside some meteorites which come from unprocessed 'carbonaceous' chondrites, microscopic grains have been detected that have much older ages up to 4.9 billion years old. These are believed to have come from dust grains produced in the atmospheres of very old stars. They were ejected into space and found their way to the cloud out of which our solar system accreted. By some process we do not understand yet, small grains manage to clump-up into progressively larger rocks and large bodies many meters and kilometers in size. As these large objects collide, they can break down again, but this time having a composition and chemistry that reflects their parentage from the larger objects.

Copyright 1997 Dr. Sten Odenwald
Return to Ask the Astronomer.