Icy impacts: Planetary scientists use physics and images of impact craters to gauge the thickness of ice on Europa
Sometimes planetary physics is like being in a snowball fight. Most people, if handed an already-formed snowball, can use their experience and the feel of the ball to guess what kind of snow it is comprised of: packable and fluffy, or wet and icy.
Using nearly the same principles, planetary scientists have been able to study the structure of Europa, Jupiter’s icy moon.