Crust (geology) formed almost immediately after formation of the Moon. Magmatism continued after the period of intense meteorite impacts ended about 3.9 billion years ago, but igneous rocks younger than 3.9 billion years make up only a minor part of the crust. Crust (geology) In geology, the crust is the outermost solid shell of a rocky planet, dwarf planet, or natural satellite. It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be distinguished based on its phase (solid crust vs. liquid mantle). The crusts of Earth, Moon, Mercury, Venus, Mars,
The Dog and Its Reflection The Dog and Its Reflection The Dog and its Reflection (or 'Shadow' in several translations) is one of Aesop's Fables and is numbered 133 in the Perry Index. An indication of how old and well-known this story was is given by an allusion to it in the work of the philosopher Democritus from the 5th century BCE. Discussing the foolish desire for more, rather than being content with what one has, he describes it as being 'like the dog in Aesop's fable.' In the story, a dog that is carrying a stolen bone, or piece of meat or cheese, looks