Project Apollo: The Moon Odyssey Explained

By Norman Ferguson

THAT’S ONE SMALL STEP FOR MAN … The Moon has always fascinated humans, and thoughts on how to get there occupied minds for hundreds of years. During the space race, setting foot on the Moon was the ultimate goal and the Apollo missions to the Moon are amongst the most successful and well-remembered manned space flights that NASA ever accomplished. In PROJECT APOLLO Norman Ferguson reveals fascinating facts and figures, and recounts amazing stories about the astronauts and their spacecraft, and how they made the giant leap for mankind.

• Language: English
• Publisher: The History Press
• Release date: May 21, 2019
• ISBN: 9780750991759

Book preview

The Moon, photographed on Apollo 11.

Structure

The Moon’s structure is similar to Earth’s in that it has an outer crust, a mantle and a core. The Moon’s crust on the near side is around 43 miles (70km) thick, with the far side’s double that.

Geological Features

The Moon certainly does not possess a smooth and polished surface, but one rough and uneven, and, just like the face of the Earth itself, is everywhere full of vast protuberances, deep chasms, and sinuosities.

Galileo, Siderius Nuncius (1610)

The terms to describe lunar features and the names of specific ones have been the subject of much discussion. Some names are officially recognised by the International Astronomical Union, founded in 1919, while others are unofficial.

Surface Composition

The Moon is covered with a layer of dust called the regolith, formed by meteorite impacts over millions of years. It can be up to 49ft (15m) deep. Amongst the rock types, igneous basalts make up most of the material found in the maria, and lighter toned anorthosites are found in the lunar highlands. Breccias were formed by rocks being fused together through meteoroid impacts.

Gardening

American scientist Harold Urey described how continual impacts erode and turn over the lunar surface as ‘gardening’.

Water

Water’s presence on the Moon was confirmed in 2009 when a Centaur booster was deliberately impacted in Cabeus crater and the ensuing ejecta analysed. The water, in ice form, is thought to be from a comet’s impact.

Colour

Depending on different lighting conditions, astronauts observed variations in surface colour. Shades of yellow, brown, grey, white, tan and black were all seen.

Man in the Moon

There liveth none under the sunne,

that knows what to make of the man in the Moone.

John Lyly, Endymion (1591)

For centuries some have seen the appearance of a human face in the lunar features:

Other figures believed to be visible in the Moon include: a rabbit, a hare, a man carrying sticks (sent as punishment for collecting them on a Sabbath), a woman weaving a pot, a crab, a toad, a lion, a fox, Judas Iscariot, and a hunchback sitting under a tree.

Crater Names

There are many thousands of craters and their names have accumulated over centuries. They can be named after notable scientists or polar explorers, as long as they are deceased. However, others have been rewarded: the Apollo 11 crew had craters in the Sea of Tranquility named in their honour.

Fifty craters are:

Alan

Alexander

Aloha

Amundsen

Anderson

Apollo

Archimedes

Babbage

Beer

Bliss

Bunsen

Byrd

Cassini

Chaucer

Curie

Cyrano

Darwin

Einstein

Freud

Geiger

Goddard

Grissom

H G Wells

Halley

Hippocrates

Hubble

Huxley

Ian

Icarus

Isabel

Ivan

Joy

Marco Polo

Marconi

Mary

Newton

Norman

Parkhurst

Robert

Schrödinger

Shackleton

Susan

Tereshkova

Titov

Tycho

Van de Graaff

Verne

von Braun

Wallace

Zhukovskiy

186 Miles

The largest crater is Bailly: its diameter is 186 miles (300km).

Impact Basins

The largest impact basin on the Moon’s visible area is Mare Imbrium (Sea of Rains) with a diameter of 731 miles (1,160km). On the far side South Pole-Aitken Basin has a diameter of 1,550 miles (2,500km) and a depth of more than 5 miles (8km).

Zap Pits

Zap pits are small craters formed by micrometeorites.

Aristarchus

Aristarchus is the brightest crater. Although only 25 miles (40km) in diameter, it is easily seen with the naked eye due to its relative brightness in Oceanus Procellarum (Ocean of Storms).

Moonquakes

Unlike Earth, the Moon does not have tectonic plate movement. However, it is seismically active and moonquakes were detected by seismometers left behind by the Apollo missions.

Mascons

Spacecraft orbiting the Moon had variations in their orbits, put down to ‘mascons’, i.e. ‘mass concentrations’. Mascons are believed to have been caused by large impacts bringing deeper and denser material closer to the surface. When it was thought mascons would lower Apollo 15’s orbit to just 33,000ft (10km) above the lunar surface, corrective action was taken.

Magnetic

The Moon does not have a significant magnetic field but evidence it once did (around 3 billion years ago) was found in returned rocks. The lack of a north or south pole made navigation harder on the surface as compasses were inoperable.

Perigee and Apogee

The Moon’s orbit around the Earth is not perfectly circular. Its furthest point is apogee and the nearest point of the oval-shaped orbit is perigee.

Orbits around the Moon use the terms apolune and perilune.

Super Moon

The term ‘Super Moon’ describes a full Moon seen at perigee. It appears 14 per cent larger and 30 per cent brighter than when seen at apogee. A full Moon at apogee is called a Micro Moon.

59 Per Cent

Due to ‘tidal locking’, the Moon always presents the same face to Earth. 59 per cent of its surface can be seen from Earth, due to ‘libration’ – the Moon’s oscillation caused by its elliptical orbit.

The Dark Side

The Moon has no ‘dark side’ but as almost half is never seen from Earth the concept of a ‘far’ or ‘dark’ side arose. It was first observed when Luna 3 took photographs in 1959. The first humans to see it directly were the crew of Apollo 8.

Lunar Months

The two most commonly used periods of describing how long it takes for the Moon to orbit Earth are:

Sidereal

The lunar orbital period with respect to the stars is 27.32166 days (27 days, 7 hours, 43 minutes, 12 seconds).

Synodic

The mean length of the synodic month, also known as a lunation, is 29.53059 days (29 days, 12 hours, 44 minutes, 3 seconds) and is the period between one new Moon and the next. A synodic month is longer than the sidereal as the Earth itself has moved its position relative to the Sun and it takes a few days for the Moon to ‘catch up’ to regain its alignment with the Sun.

Metonic Cycle

The Metonic Cycle is a period of 19 years, or 235 lunations, after which the Moon returns to exactly the same place in the sky, and its phases begin again to take place on the same day of the year.

Blue Moon

A ‘Blue Moon’ is the second full Moon in a calendar month or the third full Moon in an astronomical season (using equinoxes and solstices rather than calendar months) that has four full Moons.

Tides

The Moon’s gravitational pull causes the water on Earth to bulge, producing two tides a day. When the Sun, Moon and Earth line up, at new and full Moons, spring tides are the result – either higher than the normal high or lower than the normal low tides. They are so named not because of the season but from them ‘springing out’ and then back with increased strength. Neap tides, which occur when the Sun and Moon are at right angles to each other at quarter Moons, see high and low tides experience their smallest differences.

Land Tides

The Moon also affects land and Earth’s crust is raised, up to 12in (30cm). The crust sits on top of molten rock and this allows movement, although it is imperceptible to anyone standing on the affected area at the time.

Phases