NASA - National Aeronautics and Space Administration

It's Not Just a Good Idea, It's the Law

The Law of Superposition provides MESSENGER team scientists with the means to determine the order in which features were formed on the surface of Mercury. In this image, where north is to the top, several superposed landforms paint a complex story. The oldest feature is a near-circular crater that almost spans the entire field of view, and which is barely visible today. Later, at least three more craters were formed (one on the left, and two smaller examples on the right), before smooth plains filled all four craters. Later, a large lobate scarp cut north-south through the original crater. Later still, a simple crater formed right along the scarp — and so this crater is the youngest of those features described here. Observations like these can be used to help understand the developmental history of the innermost planet.

Date acquired: July 17, 2012

Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington