Because Jupiter is so large, it is possible to see Jupiter from Earth even without a telescope. The name comes from the ancient Romans, who named Jupiter after the main god in Roman mythology. Using a homemade telescope, Galileo made the first detailed observations of Jupiter in the year 1610 and discovered several of its larger moons. Seeing Jupiter through a telescope is really neat! If you want to see Jupiter, I recommend contacting your local amateur astronomy club. Astronomy clubs often do demonstrations and it is a great way to learn more about astronomy.

While humans have not traveled to Jupiter, NASA has sent many un-manned spacecraft to Jupiter. Currently, NASA’s Juno orbiter is exploring Jupiter and taking very detailed pictures. You can learn more about the Juno mission here.

Since Jupiter is about 310 times bigger than the Earth, asteroids or comets hit Jupiter more often than they do with Earth. Many of these strikes are unobserved, and so we don’t know anything about them. However, even amateur astronomers looking through telescopes on Earth have recorded impacts of bigger asteroids with Jupiter, and this occurs fairly often.

Callisto is said to be “dead” because there is no geological activity underneath the moon’s surface, and there are no volcanoes or earthquakes on Callisto. This means that the surface of Callisto has not changed much in 4 billion years. This is very different from the surface of the Earth. Even though the surface of the Earth appears to be constant, it is actually quite dynamic on geological timescales. The surface of the earth is constantly changing because new rock is brought to the surface and old rock is pushed down into the mantle as a result of shifting tectonic plates. This is important because the moving core of the Earth creates a magnetic field that protects the Earth from harmful solar particles. While it might be theoretically possible to “wake up” a dead planet by somehow melting the planet’s core and starting it moving, I do not know of any realistic ideas to do this.