Comets and asteroids, internal processes--where did Earth's water come from?
Plans for a manned Mars mission are getting serious, several decades after we sent humans to the moon. What has taken so long? Can it even be done?
The inner planets are small, rocky, low on moons, and ringless - yet the outer planets are huge, gaseous and icy, with rings and lots of moons. Find out why!
Learn the most tantalizing facts about this toxic, hellish world that's ironically known as Earth's sister planet!
This small, moonless, ringless planet may seem dull at first—but learn about its chaotic past, extreme temperature variations, and more interesting facts here!
Learn about Neptune's composition, moons, rings, gravity, and more! Take the quiz at the end of the article to see how much you've learned.
Take a virtual tour of Uranus to learn more about its moons, gravity, composition, rings, and more!
Wonder what Saturn's rings are made of? How much you'd weigh on Saturn? Which of its moons has lakes of methane and ethane? Find out here, and then take the quiz to see how much you've learned!
Learn about Jupiter's moons, the Great Red Spot, and Jupiter's temperature, atmosphere, gravity, and more—and then test your knowledge with a quiz!