This unusual view of the Moon's north pole was captured by the Galileo spacecraft on its way to Jupiter. The large dark regions to the left of the image are maria — remnants of ancient lava flows. Though many maria are visible on the Moon's surface, even more might be hidden below the surface, and understanding the extent of these cryptomaria is key for unlocking the history of the Moon's volcanism. You can read about how researchers use radar to search for hidden maria in our AAS Nova highlight and the associated research article in the Planetary Science Journal. [NASA/JPL/USGS]