Answer questions like ...

1. Exoplanets that have a lot of volcanic activity and exist in systems with many asteroids are bad prospects for looking for extraterrestrial life.
2. Earth and Venus are rocky planets of about the same size, but Earth's average surface temperature is about 59° F, while Venus' is 1,350° F, hot enough to melt lead or aluminum. Why the difference?
3. Earth is smack in the middle of the "habitable zone" around the sun, where temperatures are right for liquid water to exist.

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