“At most terrestrial men fancied there might be other men upon Mars, perhaps inferior to themselves and ready to welcome a missionary enterprise. Yet across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us.” So begins the H.G Wells classic science fiction novel War of the Worlds in which technologically advanced Martians invade the Earth. More than any other planet, Mars has captured the imagination of science fiction enthusiasts. Why is this?
Jupiter is the largest planet in the solar system – over ten times the size of Earth in diameter. Like the sun, it is an enormous ball of hydrogen and helium gas with smaller amounts of other elements held together by its own gravity. Although hydrogen and helium are the two lightest elements, Jupiter has so much of them that its mass is greater than the rest of the planets combined, and yet is only 0.1% the mass of the sun. The pressure of the gases increases as we dive deeper into Jupiter, and at some point, they are forced into a liquid state. But Jupiter has no solid surface.
Galileo’s most remarkable discovery happened when he pointed his telescope at the planet Jupiter. He found that Jupiter had moons! No one had conceived of the possibility that other planets could have moons that orbit the planet, just as Earth’s moon orbits Earth.
Known for its stunning system of rings, Saturn is truly a gem of the solar system. Although Jupiter, Uranus, and Neptune also have rings, only Saturn’s are easily visible from Earth and are an icon of astronomy. Yet these rings were unknown until the 1600s. For the first five and a half millennia, Saturn was simply the slowest of the five “wandering stars.” The invention of the telescope in 1608 paved the way for more advanced telescopes, eventually allowing astronomers to see Saturn in all its splendor.
Saturn has 82 known moons – more than any other planet at the publication time of this article. Of these, twenty were discovered in the last year. Most are just a few miles across. But the larger ones are some of the most fascinating moons of the solar system.