Water covers around three-quarters of Earth, and it can be found on other worlds of the Solar System, including sub-surface deposits of ice on Mars. One of the great questions in planetary science today is attempting to understand how water came to exist on the surface of planets, including Earth. Water forms naturally during the course of many chemical reactions, so one possibility is that water was created during chemical reactions in the early solar system. Another possible explanation is that water was delivered to the surface of planets through collisions with comets — which are, essential, dirty snowballs in…
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