Hot Rock

Meteorites Land Cold

Few meteorites have been collected immediately after they fell, and reports vary from “hot” to “cold.” The physics of the process, however, lead scientists to favor “cold” to perhaps a bit warm for the smallest meteorites. Outer space is exceedingly cold. A meteoroid in space is very cold. The incandescent (glowing) period of a meteor is only a few seconds and during the few minutes of subsequent “dark fall” the meteor is falling through cold atmosphere. Although the exterior gets hot enough to melt during the incandescent phase, the hot material immediately ablates away, so conduction of heat to the inside of the rock is inhibited. Also, rocks are not good conductors of heat. Meteorites don’t start fires. The interior of a meteorites shows no evidence of having been heated during the atmospheric entry process.

Backscattered-electron image of lunar meteorite PCA 02007. At the top and right is the glassy, vesicular fusion crust that occurs on the outside of the meteorite. Note the sharp contact between the crust and the interior, which did not get hot enough to melt. Image credit: Ryan Zeigler