Discover our Solar System

Although we know a lot about the planets in our solar system, we have much more to learn. Scientists want to know more about the composition of the planets and their atmospheres. Some people wonder whether life ever existed on these lonely outposts.

Solar System

One way for scientists to learn more is by sending unmanned spacecraft to the other planets. The Galileo Jupiter orbiter spacecraft was launched on October 18, 1989, to explore Jupiter and its satellites. Click on Galileo to learn more about this spacecraft and its mission. Then answer the questions.

Galileo carried a probe that was used to evaluate Jupiter's ________.

rings     moons     atmosphere


Galileo has shown that Jupiter's rings are formed by dust caused by meteorites colliding with ________.

Jupiter's inner moons     unmanned spacecraft     the Sun


Now let's examine another spacecraft whose voyage to Saturn has revealed much about the ringed planet and its many moons. Click on Cassini to learn more about this mission. Then answer these questions:

What is the closest Cassini can get to Saturn’s moons during targeted flybys?

16 miles     86 miles     226 miles

How many moons have been discovered in orbits around Saturn?

3     62     117


For centuries people have wondered whether there is other life in our solar system. You may be surprised to learn that some scientists believe there may be.

What evidence found on a meteorite suggests that there was once life on Mars?

fossilized plant life

bacteria-like organisms

frozen fresh water

Press the button to see how well you did.  

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