E.T., Stitch, Chewbacca, Groot — humans have a lot of ideas about what aliens might look like. But what is the science behind extraterrestrial life? Is it possible that humans will ever experience "first contact" with an alien species?
Many scientists hope so. They're looking for extraterrestrial life on planets with conditions that look like Earth's. A life-friendly planet would probably have water, for example. And for water to be a liquid, the planet must be the perfect distance from its sun for that water not to freeze or turn into a gas.
There's no evidence yet for life on other planets, but as scientists discover more and more planets outside our solar system, they're hopeful that some of these worlds will be "just right" for life to exist or evolve there.
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