Exploratour - Evolution of the Solar System
Things which came along and hit the surfaces of the planets may have included comets. Thus, comets may have brought elements of an atmosphere to the each of the inner planets.
One comet the size of Halley's comet would bring enough water to form a large lake!
Read more about comets by reading our comet section. Read more about comet crashes by taking the Exporatour of Spectacular Crashes in the Solar System, at the bottom of this page.
This is page 25 of 60