We live in a Cosmic "shooting gallery". Objects inhabiting our Solar System have been profusely and mercilessly blasted by showering asteroids and comets for billions and billions of years. However, planets and large moons have their way of smoothing away the scars--their strong gravity pulls them into a nice ball-like spherical shape. Furthermore, some of these larger spheres possess sufficient internal heat to cause flows of fiery lava and other volcanic features that can fill in the scars of impact craters. A few such large bodies are blasted by strong winds and pouring rains, which also erode away the pockmarks left on their surfaces by showering impactors.
In addition, the newly collected data derived from the GRAIL mission helps astronomers redefine the late heavy bombardment--a proposed episode that occurred about 4 billion years ago, during which a heavy shower of projectiles pelted the bodies of the inner Solar System, including Earth and its beloved Moon, creating heavy lunar cratering in the process. The concept of the late heavy bombardment is primarily based on the ages of massive near-side craters that are either within, or adjacent to, dark, lava-flooded basins (lunar maria), that are named Oceanus Procellarum and Mare Imbrium. However, the composition of the material existing on and below the surface of the lunar near-side indicates that the temperatures beneath this area are not representative of Earth's Moon as a whole at the time of the late heavy bombardment. The difference in the temperature profiles may have caused scientists to overestimate the amount of crater-excavating projectiles that characterized the late heavy bombardment. New studies by GRAIL scientists indicate that the size distribution of impact craters on the lunar far-side is a more accurate reflection of the crater-forming history of the inner Solar System than those pock-marking the near-side.
Cassini wasn't originally designed to spot signs of life in the Enceladus plume. In fact, planetary scientists didn't even know that the plume existed until after the spacecraft reached Saturn.