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Learn about planets outside our solar system through Exoplanets and Alien Solar Systems by Tahir Yaqoob, Ph.D., a book in our online store book collection.

The Goldilocks Theory

Just as Goldilocks found the porridge that was just right, the Earth seems to be just right for living creatures. The Earth seems to be the perfect distance from the sun for lots of water.

Venus is too close to the sun, and too hot for flowing water on its surface. In fact, it is so hot that, like a sauna, all the water has been evaporated into the atmosphere, and Venus has a thick and heavy atmosphere.

Mars is too far from the sun, and too cold for flowing water on its surface. Mars also has no continental drift, so particles of the atmosphere which become trapped within the ground stay trapped within the ground. Thus over time the atmosphere of Mars has become thin, and all the water is frozen into the ground.

The temperature of Earth is just right for flowing water on the surface, and for the rock which allows for continental drift. With continental drift, particles of the atmosphere which become trapped within the ground are brought back to the atmosphere through eruptions of volcanoes. These conditions cause refreshment of the planet's atmosphere and help keep the temperature just right. These conditions are just right for abundant life.

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Earth's Early Ocean

Once the Earth began to cool, water vapor, one of the volatiles, began to condense and form an ocean. According to the Goldilocks theory, Earth is at just the right distance from the sun for the temperature...more

The Climate of Mars

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Volcanic Ash

Ash is formed as a volcano erupts when rocks made by the volcano blow apart into millions of tiny pieces. The rocks are still very hot, because they just formed from lava. If the hot rocks come into contact...more

Cinder Cones

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Flowing Lava

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How Do Plates Move?

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Clues to Plate Movements

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA