Many hundreds of glaciers have been discovered on Mars in the middle latitudes, their ice hidden from view. They appear to be remnants of previous climates where snowfall and ice accumulation was stable at these latitudes, forming glaciers as we see on Earth in the polar regions. Through a process that is not yet understood, the martian glaciers were covered with a thin veneer of rock and dust that has subsequently preserved them for millions of years. Due to the extreme cold, these Martian glaciers currently move at imperceptibly slow rates. Earth also exhibits a variety of “debris-covered glaciers” whose history and inner workings have eluded scientists, but are much more accessible for study. For both Earth and Mars, we use radar to probe into the subsurface and map their ice content and structure. At Mars, this is accomplished with NASA’s Mars Reconnaissance Orbiter, while on Earth we are able to conduct geophysical studies on the surface and from airplanes. Through a combination of many types of measurements we are beginning to understand these enigmatic features on both Earth and Mars in a new way.