Astronomy
The Impact of Comets on Planetary Evolution
Quick fact
A single comet the size of a small mountain can contain as much water as a large lake, and during the early solar system, comet impacts may have delivered enough water to fill Earth's oceans many times over.
Why this is interesting
We often think of comets as spectacular but rare visitors, yet without them, our planet might be a dry, barren rock. Could these icy wanderers have seeded Earth with the very ingredients of life?