How the Moon Works

Geologic History of the Moon

Based on analyses of the rocks, crater densities and surface features, geologists came up with the following geologic history of the moon:

1.     After the impact (about 4.45 billion years ago), the newly formed moon had a huge magma ocean over a solid interior.

2.     As the magma cooled, iron and magnesium silicates crystallized and sank to the bottom.Plagioclase feldspar crystallized and floated up to form the anorthosite lunar crust.

3.     Later (about 4 billion years ago), magma rose and infiltrated the lunar crust, where they reacted chemically to form the basalt. The magma ocean continued to cool, forming the lithosphere (which is like the material in the Earth's mantle). As the moon lost heat, the asthenosphere (the next layer in) shrank toward the core and the lithosphere became very large. These events led to a model of the moon's interior that is very different from that of the Earth. Lunar Behavior The moon is thought to influence our daily life and moods, possibly even causing odd behavior. In fact, it's the inspiration for the word "lunatic." Werewolf aficionados, of course, know that a full moon triggers terrifying transformations. And hospital and emergency personnel tell of more crimes, accidents and births during a full moon -- but the evidence for this is mostly anecdotal rather than statistical.

4.     From about 4.6 to 3.9 billion years ago, the moon was intensely bombarded by meteors and other large objects. These impacts modified the lunar crust and gave rise to the large, densely cratered surface in the lunar highlands. Some of these bombardments produced large, multi-ringed basins and mountains.

5.     When the bombardment ceased, lava flowed from the inside of the moon through volcanoes and cracks in the crust. This lava filled the maria and cooled to become the mare basalts. This period of lunar volcanism lasted from about 3.7 billion years to 2.5 billion years ago. Much of the moon's heat was lost during this period. (Because the moon's crust is slightly thinner on the side that faces the Earth, lava could erupt more easily to fill the maria basins. This explains why there are more maria on the near side of the moon compared to the far side.)

6.     O­­nce the volcanic period ended, most of the moon's internal heat was gone, so there was no major geologic activity -- meteor impacts have been the only major geologic factor at work on the moon. These impacts have not been as intense as in earlier periods of the moon's history; bombardments have generally been declining throughout the solar system. However, the meteoric bombardment that continues today has produced some large craters on the maria (like Tycho and Copernicus) and the fine regolith (soil) that covers the lunar surface.

Let's look at some of the phenomena involving the moon's orbit.

How the Moon Works

by Craig Freudenrich, Ph.D.

Giant Impactor Hypothesis

At the time of Project Apollo in the 1960s, there were basically three hypotheses about how the moon formed.

·         Double planet (also called the condensation hypothesis): The moon and the Earth formed together at about the same time.

·         Capture: The Earth's gravity captured the fully formed moon as it wandered by.

·         Fission: The young Earth spun so rapidly on its axis that a blob of molten Earth spun off and formed the moon.

But based on the findings of Apollo and some scientific reasoning, none of these hypotheses worked very well.

·         If the moon did form alongside the Earth, the composition of the two bodies should be about the same (they aren't).

·         The Earth's gravity isn't sufficient to capture something the size of the moon and keep it in orbit.

·         The Earth can't spin fast enough for a blob of material the size of the moon to just spin off.

Because none of these hypotheses was satisfactory, scientists looked for another explanation. In the mid-1970s, scientists proposed a new idea called the Giant Impactor (or Ejected Ring) hypothesis. According to this hypothesis, about 4.45 billion years ago, while t­he Earth was still forming, a large object (about the size of Mars) hit the Earth at an angle. The impact threw debris into space from the Earth's mantle region and overlying crust. The impactor itself melted and merged with the Earth's interior, and the hot debris coalesced to form the moon. The Giant Impactor hypothesis explains why the moon rocks have a composition similar to the Earth's mantle, why the moon has no iron core (because the iron in the Earth's core and impactor's core remained on Earth), and why moon rocks seem to have been baked and have no volatile compounds. Computer simulations have shown that this hypothesis is feasible.

MOON FACTS

Distance from Earth: 240,250 miles (384,400 km)

Diameter: 2,160 miles (3,476 km), or about 27 percent of the Earth’s diameter

Mass: 7.35 x 10²² kilograms, about 1.2 percent of the Earth’s mass

Gravity: 1.62 m/s², or 16.6 percent of the Earth’s gravity

Mean surface temperature:

sunlight = 266 F (130 C),

shadow = -292 F (-180 C)

Atmosphere: None

Orbital period: 29.5 day

Lunar day: 29.5 Earth days (the moon is tidally locked to the Earth, so our gravity drags the moon around on its axis and the same side of the moon always faces Earth)

What's on the surface of the moon?

As we mentioned, the first thing that you'll notice when you look at the moon's surface are the dark and light areas. The dark areas are called maria. There are several prominent maria.

·         Mare Tranquilitatis (Sea of Tranquility): where the first astronauts landed

·         Mare Imbrium (Sea of Showers): the largest mare (700 miles or 1100 kilometers in diameter)

·         Mare Serenitatis (Sea of Serenity)

·         Mare Nubium (Sea of Clouds)

·         Mare Nectaris (Sea of Nectar)

·         Oceanus Procellarum (Ocean of Storms)

The maria cover only 15 percent of the lunar surface.

The remainder of the lunar surface consists of the bright highlands, or terrae. Highlands are rough, mountainous, heavily cratered regions. The Apollo astronauts observed that the highlands are generally about 4 to 5 km (2.5 to 3 miles) above the average lunar surface elevation, while the maria are low-lying plains about 2 to 3 km (1.2 to 1.8 miles) below average elevation. These results were confirmed in the 1990s, when the orbiting Clementine probe extensively mapped the lunar surface.

The moon is littered with craters, which are formed when meteors hit its surface. They may have central peaks and terraced walls, and material from the impact (ejecta) can be thrown from the crater, forming raysthat emanate from it. Craters come in many sizes, and you'll see that the highlands are more densely cratered than the maria.

Another type of impact structure is a multi-ringed basin. These structures were caused by huge impacts that sent shockwaves outward and pushed up mountain ranges. The Orientale Basin is an example of a multi-ringed basin.

Besides craters, geologists have noticed cinder cone volcanoes, rilles (channel-like depressions, probably from lava), lava tubes and old lava flows, which indicate that the moon was volcanically active at some point.

The moon has no true soil because it has no living matter in it. Instead, the "soil" is called regolith. Astronauts noted that the regolith was a fine powder of rock fragments and volcanic glass particles interspersed with larger rocks.

Upon examining the rocks brought back from the lunar surface, geologists found the following characteristics:

1.       The maria consisted primarily of basalt, an igneous rock derived from cooled lava.

2.       The highland regions include mostly igneous rocks called anorthosite and breccia

3.       If you compare the relative ages of the rocks, the highland areas are much older than the maria. (4 to 4.3 billion years old versus 3.1 to 3.8 billion years old).

4.     The lunar rocks have very little water and volatile compounds in them (as if they've been baked) and resemble those found in the Earth's mantle.

5.       The oxygen isotopes in moon rocks and the Earth are similar, which indicates that the moon and the Earth formed at about the same distance from the sun.

6.       The density of the moon (3.3 g/cm³) is less than that of the Earth (5.5 g/cm³), which indicates that it doesn't have a substantial iron core.

Astronauts placed other scientific packages on the moon to collect data:

·         Seismometers didn't detect any moonquakes or other indications of plate tectonic activity (movements in the moon's crust)

·         Magnetometers in orbiting spacecraft and probes didn't detect a significant magnetic field around the moon, which indicates that the moon doesn't have a substantial iron core or molten iron core like the Earth does.

Let's look at what all of this information tells us about the formation of the moon.

The Moon's Magical Phases

Each phase of the Moon resonates with magical significance and astrological meaning.

These meanings spill out into world-wide folklore, sinister superstitions, and even gardening advice. Werewolves, in particular, are creatures of the Moon  – transforming themselves by the light of the full Moon into deadly hunters which can only be killed by a silver bullet. Hairy, scary creatures aside….the Moon’s phases are used in witchcraft and magic to determine when to cast a certain kind of spell. New Moons are for beginnings, for example, while the waning Moon is believed to be a good time for banishing things, or clearing negative influences. In predictive astrology these phases reveal different themes in your life, and offer a guide to planning activities, projects, and even study. If you want to try tuning in to these phases you’ll need to observe the Moon every evening, cloud permitting, and check exact details of its phase in an almanac or moon calendar.

Here are the phases and what they mean:

The New or Crescent Moon - Beginnings

It’s time to begin projects, new regimes, fresh starts. Some gardeners maintain that this is the best time to plant seeds – you can easily imagine that this is a symbol for many things.

The First Quarter Moon - Action

The Moon reaches her first quarter seven days after the New Moon. Take your projects out there and do something practical about those decisions or wishes you made when the Moon was new.

The Gibbous Moon – Movement

The Moon is now waxing larger as it moves from New towards Full. The next seven days have a forward momentum. If you began something new, like a diet, at the New Moon, you should be seeing some results by now. Not the final results you imagined, but moving towards them.

The Full Moon – Harvest



The lunar energies peak now, fourteen days into the cycle. It is harvest time, possibly for projects begun at a New Moon months beforehand. Results in just two weeks are hard to find in most endeavors’……although we can always dream. Emotions may peak one way or another too.

The Disseminating Moon – Thinking

The Moon begins to wane, and energies and thoughts turn inwards. This is a good time to think about your projects or the direction you are following. Use what you have learned and bide your time.

The Third Quarter Moon – Shuffling the deck

If you need to fine-tune things, now’s the time. It’s about seven days since the Full Moon. Work with what you have, and make it better. It’s not a good time to go after anything new, but a great time to polish up your skills and make things work out. Anything you don’t need, or which isn’t working can be recycled or thrown out now. Needless to say, this is a good time to clear out cupboards, weed your garden, or get a sassy new haircut.

The Balsamic Moon - Release

The waning Moon has reached its last phase. It is a time of release. If you want to let go of a relationship, job, or anxiety this is the perfect time to focus on this desire. You may feel peaceful, or empty. The final days just before the New Moon are also called the dark of the Moon, because it sheds so little light. Symbolically, this suggests the inner world is more important than the outer world at this point in the cycle.