Apogee The point in the Moon’s orbit when it is farthest away from the Earth.

Apollo 11 The mission that first put men on the Moon. The Lunar Module of Apollo 11 touched down on 20th July 1969. US astronauts Neil Armstrong and Buzz Aldrin were the first people to walk on the Moon.

Basin A large dip in the surface of the Moon. 

Crater A saucer-shaped dip on the surface of the Moon (and other worlds). The Moon's craters are impact craters, formed when asteroids and comets collided with the Moon billions of years ago. Impact craters are also found on the surface of other moons, asteroids and planets, including Earth.

Crescent Moon A phase of the Moon that occurs just before and after every New Moon. A Crescent Moon appears as a small curved sliver of light.

Earthshine Sunlight reflected from the Earth and on to the Moon’s surface. The reflected light makes the dark surface of the Moon appear to glow.

Full Moon A phase of the Moon. During a Full Moon, the visible side of the Moon is turned towards the Sun which lights it up so that it appears as a full disc of light.

Gibbous Moon A phase of the Moon that occurs between Quarter Moon and Full Moon. The Moon appears as an oval of light.

Luna Programme A Russian space project that sent several space probes to the Moon. In 1959, the Luna 2 became the first man-made object to touch the Moon. In the same year, the Luna 3 took the first photographs of the far side of the Moon.

Lunar A word that means “about the Moon”.

Lunar eclipse The passage of the Earth between the Sun and Moon during which the Earth casts a shadow on the Moon.

Lunar month The time it takes the Moon to pass from New Moon to New Moon—about 29.5 days.

Mare A smooth lava plain on the surface of the Moon, formed when lava from ancient eruptions turned to solid rock. To the observer, it appears as a dark patch. Mare is the Latin word for sea. This is because early astronomers believed the plains were seas.

Moon A ball of rock that travels around the Earth. It is the brightest object in the night sky, although it does not give out its own light, but reflects light from the Sun. The Moon is about 4.53 billion years old. It may have formed when a large object crashed into the young Earth and the resulting debris came together to form our Moon. There is neither air nor liquid on the Moon. It is a barren world, made up of craters, mountain ranges, and wide lava plains. The Moon spins once on its axis in exactly the time it takes it to orbit the Earth. This means that we only ever see one side of the Moon.

New Moon One of the phases of the Moon. A New Moon occurs when the Moon lies roughly between the Sun and the Earth so that the side facing us does not reflect any light.

Perigee The point in the Moon’s orbit when it is closest to the Earth.

Phase The different appearance of Mercury, Venus, or the Moon as they move around their orbits. The lunar phases refer to our changing view of the Moon throughout the month. The Moon appears to change shape because our view of its sunlit part changes. When the face pointed towards us is turned away from the Sun we cannot see the moon at all. This is called a New Moon. When it is turned fully towards us we see a Full Moon. In between these phases it passes through crescent, quarter and gibbous phases.

Quarter Moon One of the phases of the Moon. In a Quarter Moon, only half of the visible side of the Moon is lit up.

Regolith A layer of loose dust, soil and rock that covers harder layers of rock. It is found on many moons and asteroids.

Rilles Cracks, or channels, that run across the smooth parts of the Moon, probably caused by ancient volcanic eruptions.

Selenography The study of the surface of the Moon.

Terrae The light areas on the Moon as we can see it from Earth. These are highlands of mountains.

Waning A word that means “shrinking”. This happens to the Moon during the period between a Full Moon and a New Moon, when the visible part of the Moon becomes smaller and smaller.

Waxing A word that means “growing”. This happens to the Moon during the period between a New Moon and a Full Moon, when the visible part of the Moon becomes larger and larger.

Consultant: Mike Goldsmith