Crescent Europa
Although the phase of this moon might appear familiar, the moon itself might not. In fact, this crescent shows part of Jupiter 's moon Europa . The passing robot spacecraft Voyager 2 captured this image in 1979. Visible are plains of bright ice , cracks that run to the horizon, and dark patches that likely contain both ice and dirt. Raised terrain is particularly apparent near the terminator , where it casts shadows . Europa is nearly the same size as Earth's Moon , but much more smooth, showing few highlands or large impact craters . Evidence and images from the Galileo spacecraft , currently orbiting Jupiter , indicate that liquid oceans might exist below the icy surface. To test speculation that these seas hold life, NASA has started preliminary development of the Europa Orbiter , a spacecraft that would use radar to help determine the thickness of the surface ice. If the surface ice is thin enough, a future mission might drop hydrobots to burrow into the oceans and search for life.