1. Neptune has the third largest mass of all of the planets, but Uranus has the third largest diameter. Reconcile these two facts. 2. Discuss why astronomers believe that Europa, Ganymede, and...

1. Neptune has the third largest mass of all of the planets, but Uranus has the third largest diameter. Reconcile these two facts.

2. Discuss why astronomers believe that Europa, Ganymede, and Callisto may harbor some sort of marine life. Why do they not expect any life on the surfaces of these worlds?