| A | B |
|---|
| Crescent moon | Moon phase with less than one-half of the side facing Earth illuminated. |
| Diameter | The distance across a circle through its center. |
| Erosion | The wearing away of a planetary surface by some natural process such as lave flow, bombardment, wind, water or another mechanism. |
| First Quarter Moon | Moon phase between the new and full moon where exactly half of the side facing Earth is illuminated |
| Full Moon | A phase of the Moon in which the entire side facing Earth is illuminated by sunlight. |
| Geologist | A scientist who studies the formation, structure, history, and processes that change the Earth and other planetary bodies. |
| Gibbous Moon | Moon phase occurring when more than half of the side facing Earth is illuminated. |
| Impact Crater | A circular depression in the ground caused by meteoroids or asteroids hitting the surface of a planet |
| Lunar | Relating to the moon |
| Meteoroid | A small solid body moving through space in orbit around the Sun. |
| Moon | The proper name of the object that orbits around the Earth |
| Moon Phases | The monthly changes in the appearance of the Moon as seen from the Earth. |
| New Moon | A phase of the Moon in which the side facing the Earth is not illuminated by the Sun. |
| Third Quarter Moon | Moon phase between the Full and the New Moon where exactly half of the side facing Earth is illuminated |
| Waning | This occurs when the amount of light reflected off the Moon to Earth is decreasing. |
| Waxing | This occurs when the amount of light reflected off the Moon to Earth is increasing. |
| Weathering | The action of elements in altering the color, texture, composition, or form of exposed objects on the surface of a planet or Moon. |
