Most achondrites collected on Earth are derived from asteroids, but one small group is thought to come from Mars and another from the Moon. ... Johnstown meteorite. Sawed and polished section of a fragment of the Johnstown meteorite, an achondrite that was seen to fall July 6, 1924, in Colorado.

How are achondrites made?

An achondrite is a stony meteorite that does not contain chondrules. It consists of material similar to terrestrial basalts or plutonic rocks and has been differentiated and reprocessed to a lesser or greater degree due to melting and recrystallization on or within meteorite parent bodies.

How do chondrules form?

Formation. Chondrules are believed to have formed by a rapid (flash) heating (within minutes or less) and melting of solid dust aggregates of approximately Solar composition under temperatures of about 1000 K. These temperatures are lower than those under which CAIs are thought to have formed.