Compton-Belkovich This image from the Lunar Reconnaissance Orbiter captures a unique dome in the Compton-Belkovich region, a clue to the site's volcanic past. This region is rich in thorium, a radioactive metal. Evidence points to a concealed granitic batholith below the surface of this hot spot on the far side of the Moon. The sunlight in this picture is coming from the SSW, and this image spans approximately 510 meters across. NASA / GSFC / Arizona State University