Moons and Solar System Debris After completing this section, students will differentiate between meteors, meteorites, comets and asteroids (Standard PI-079)

Bodies that travel around other planets are called satellites. Except for Venus and Mercury, all the other planets have at least one satellite

The moon is the Earth’s only satellite. Mars has two moons, Phobos and Diemos. Both have irregular shapes and are covered with impact craters

Jupiter has 28 moons. The four largest are called the Galilean Moons They are named after their discoverer, Galileo Galilei

Io, the closest moon to Jupiter is geologically active. Io has an iron core with a sulfur dioxide atmosphere

Europa has a smooth and shiny surface caused by ice At one time, life forms might have developed on Europa

Ganymede is the largest moon in the solar system It is composed of a rocky core surrounded by ice. It is also the only moon with a magnetic field

Callisto is the most heavily cratered moon. It also has oxygen in it’s atmosphere Callisto might also have a subsurface ocean of saltwater

Saturn has at least 24 moons. The largest is Titan Titan has a nitrogen based atmosphere, like Earth. It’s average temperature is about –180C

Uranus has 21 moons. The 5 biggest are Titania, Oberon, Umbriel, Ariel and Miranda They all lack atmospheres and have impact craters

Neptune has 8 moons. Triton is the biggest Titan has ice caps made of methane and ammonia. Triton also has ice volcanoes

The solar system consists of the sun, planets, and moons. But there are other objects in our solar system

Comets and TNOs

Comets are described as dirty snowballs. They are made of dust particles trapped in a mix of water, carbon dioxide, methane and ammonia They spend most of their orbit outside of the solar system.

TNO – Trans Neptunian Objects Huge numbers of comets orbit in the outer reaches of our solar system in a region called the Kuiper Belt.

Asteroids – solid rocklike masses with irregular shapes Scientists think they came from material left over from the solar system formation

Other objects in the solar system include: Meteoroids – a rock or ice fragment traveling in space (smaller than asteroids) Meteors – light made by a meteoroid as it passes through the earth’s atmosphere (can occur in large numbers – meteor shower) Meteorites – a part of a large meteoroid that survives the trip through the atmosphere and strikes the Earth