Chunks of this planetary material sometimes collide with Earth and become meteorites themselves. There is strong evidence that a very few meteorites even come from Mars, providing our only rock samples from another planet. Meteorite Classifications Scientists roughly classify meteorites into stones, irons, and stony-irons. Stones are further subdivided into chondrites and achondrites. The SJC meteorite is a chondrite.
Chondrites have a composition that closely resembles that of the photosphere of the sun.
Scientists believe that many chondrites formed during the early stages of the solar system. Once in the atmosphere, air friction slowed the falling rock while heating it white hot. During this time of intense heating, thermal streesses may have cracked the rock and caused it to break apart. As the rock slowed down due to air friction, the ablation slowed and eventually stopped. By then the rock was falling nearly straight down.