Exploratour - Evolution of the Solar System
Comets range in size from 10 km to 100 km in diameter, which can be thought of as a pretty large container of material. Since comets are made mostly of water, the impact of a comet with the primitive Earth would have deposited a large amount of water for the atmosphere and ocean. Since comets are only loosely held together, like a snowball, it could burn up at high elevations and deposit its water into the atmosphere. One comet the size of Halley's comet would bring enough water to form a large lake. In recent years some evidence has surfaced that many small comets may be hitting the Earth all the time, bringing water and other molecules.
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.
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