Europa is one of the moons that revolve around Jupiter. A thick sheet of ice covers its entire surface. Many scientists believe that the ice is covering an ocean of water, and that it is possible for life to exist on Europa under the thick ice sheet. Recently, using the Hubble Space Telescope, astronomers spotted water vapor clouds breaking out through Europa's surface. This provided the scientists with a sign that an ocean exists under the ice sheet. Which of the following would best support the theory that life exists on Europa?
A) revolution of Europa around Jupiter
B) presence of water vapor in Europa's atmosphere
C) presence of thick ice sheets on Europa's surface
D) direct evidence of liquid water just below Europa’s surface