Mercury's Caloris impact

Mercury

. When an exceptionally large meteorite hit Mercury an estimated 3.85 billion years ago, it sent intense waves around the planet and through its core. They came to a focus on the opposite side of Mercury, disrupting the surface and producing hilly and lineated terrain there. The Caloris Basin was excavated at the impact site, and it now exhibits concentric waves that froze in place after the impact (Fig. 2.19).

Copyright 2010, Professor Kenneth R. Lang, Tufts University