Meteors and meteorites hit planets from time to time, and add some minerals to the planet's core. While meteorites usually only bring small amounts of minerals and don't harm anything, large meteors generally bring big amounts with them. However, they'll also make massive damage on the planet. Normally, everyone gets a message when a large meteor hits a planet.

This is a testing version.
It may be incomplete, and have more bugs (or features) than the public live version at planetscentral.com.