Water Worlds May Hide Water Underground Summary

A population study of 43 exoplanets orbiting M-dwarf stars used both the transit method and radial velocity method to find the densities of the worlds and a surprising pattern emerged. The planets are less dense than expected, suggesting they are not purely rock but half-rock and maybe half-water. Plus, star factories in the Milky Way, glaciers on ancient Mars, and This Week in Space History.