Shop Windows to the Universe

Become a nitrogen atom in the nitrogen cycle in our Traveling Nitrogen Classroom Activity Kit/Game. See all our games, activity kits and classroom activities.

Exploratour - The Archean Age

This drawing represents a comet bringing atmospheric molecules and possibly primitive life forms to the Earth's surface.
Click on image for full size
JPL/NASA

As well as being hit by debris and smaller, leftover planetismals, the planets in the inner solar system may have also been hit by comets. Craterchains found on moons show that comets have hit a planet before. And comet Shoemaker-Levy 9 hit and plunged into the planet Jupiter in 1995. 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. One comet the size of Halley's comet would bring enough water to form a large lake. Since the Earth had lost its original atmosphere, comets are a potential source of the replacement atmosphere.

Scientists believe it is possible that life may have begun on these distant, solar system traveling objects. Out in their distant home, the Oort Cloud, comets are exposed to the kind of energy needed to form the long, complex molecules of which life is thought to begin with. Thus, the crash of a comet onto the surface may have also brought the elements of life to the Earth.

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.

Shop Windows to the Universe Science Store!

Our online store includes books on science education, ranging from evolution, classroom research, and the need for science and math literacy!

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

ExploraTour - Looking at the World in a Different Light

Even though the sleeping man is no longer on the bed, you can still see where he was lying down. The heat from his body warmed up the bed sheets which are now radiating infrared light toward your eyes....more

ExploraTour - Looking at the World in a Different Light

All warm objects radiate in the infrared. The warmer the object, the higher the frequency and intensity of the radiation. Very hot objects give off other types of radiation in addition to infrared. Click...more

ExploraTour - Looking at the World in a Different Light

Your eye is a wonderful detector of visible light. Different frequencies of light produce different sensations in the eye which we interpret as colors. Our eyes detect light by using light sensitive components...more

ExploraTour - Looking at the World in a Different Light

Imagine you found a pair of special glasses that not only gave you telescopic vision but gave you the ability to see all forms of radiant energy. The universe in visible light contains all the familiar...more

ExploraTour - Looking at the World in a Different Light

This is a volcano on the island of Miyake in Japan. It has erupted, sending hot lava and ash into the air, a total of ten times. The time after one eruption until the next occurred was about twenty years...more

ExploraTour - Looking at the World in a Different Light

The awesome power of a giant black hole was revealed by looking at this galaxy in three different types of light. The picture that you see is of Centaurus A, a very peculiar galaxy. A galaxy is just a...more

ExploraTour - Looking at the World in a Different Light

This is a plant in Gary, Indiana where power is made. We use power to run things like television sets, radios, lights, and microwave ovens. The picture looks very strange because it was taken in infrared....more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF