| A | B |
|---|
| asteroids | Small, solid, rocky bodies that orbit close to the Sun. |
| gas giants | The four largest planets—Jupiter, Saturn, Uranus, and Neptune—that are made mainly |
| tectonics | The processes of change in a crust as a result of the motion of hot material underneath. |
| meteor | When a particle enters Earth’s upper atmosphere and the particle and the air around it |
| meteorite | A space object that passes through Earth’s atmosphere and reaches Earth’s surface. |
| astronomical unit | Earth’s average distance from the Sun. |
| comet | A small, icy object that produces a coma when it gets close to the Sun. |
| volcanism | A process that moves molten rock from a planet’s interior onto its surface. |
| ellipse | The shape of the planets’ orbits in our solar system. |
| terrestrial planets | Small, solid, rocky bodies that orbit close to the Sun. |
| ring | A wide, flat zone of small particles around a planet’s equator. |
| tectonics | This process shaped mountains, valleys, and other features on Earth and other space bodies. |
| astronomical unit | This is equal to about 150,000,000 kilometers. |
| ellipse | flattened circle or oval |
| volcanism | This is the eruption of molten material onto a planet’s surface. |
| gas giants | The four largest planets in the solar system |
| meteor | These are found far from the Sun, so they are made of different ices as well as rock and some metal. |
| comets and moons | These are found far from the Sun, so they are made of different ices as well as rock and some metal. |
| terrestrial planets | The closest planets to the Sun—Mercury, Venus, Earth, and Mars—that all have rocky |
| asteroids | Most of these have paths that keep them between the orbits of Mars and Jupiter. |
