This episode examines questions surrounding the possibility that life exists on other planets. What would aliens look like? Are planets that could harbor life rare or common in the universe? Are "aliens" already among us on planet Earth?

The resources below provide supplementary articles and media on evidence of prerequisite conditions for life on planets other than the Earth, on recent discoveries of planets beyond our solar system, and the search for life in the universe.

		Liquid Mars Article for grades 6 through 12 In March 2004, two NASA explorers discovered firm evidence that water once flowed on Mars—perhaps enough water to harbor life. Examine their findings and the enduring allure of the red planet.
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		Water on Mars? Article for grades 9 through 12 News that the Mars Global Surveyer showed evidence of liquid water on Mars caused quite a buzz. Why? Liquid water is the "smoking gun that tells us Mars has all the elements for life."
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		Fossil Microbes on Mars? Article for grades 9 through 12 A meteorite that escaped from Mars 16 million years ago was found recently in Antarctica. Does it, or doesn't it, hold evidence that proves the existence of life on the red planet?
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		Astro Viz: Extrasolar Planets Article for grades 6 through 12 Since 1995, astronomers have discovered more than 100 planets orbiting stars beyond our Sun—only a fraction of those thought to exist. Take an interactive tour of the Milky Way Galaxy to visit these "exoplanets."
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		Beyond Our Solar System: Searching for Extrasolar Planets Article for grades 9 through 12 Stars are about one billion times brighter than any orbiting planet. Learn how scientists are now discovering extrasolar planets despite this overwhelming brightness.
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		Carl Sagan and the Quest for Life in the Universe Article for grades 9 through 12 Cosmos, Contact, Icarus and Billions and Billions—from TV and movies to professional journals and best-selling books, Carl Sagan's influence was legendary.
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		The Search for Life: Are We Alone? Educator's Guide Curriculum Materials for grades 6 through 12 Are we alone in the universe, or does life exist elsewhere? Get ready to be immersed in the museum's Space Show, where cutting-edge technology is used to communicate cutting-edge science.
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		The Search for Life: Are We Alone? Educator's Guide Insert Activity for grades 6 through 12 Life exists on Earth because of the favorable balance of water, elements, and other conditions. What would happen if the balance changed? And what role did the formation of the solar system play?
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