the moon..history, features, and effects. (teach)

http://www.areavoices.com/ photo courtesy of Bob King

Our Favorite

Little Satellite

The MoonIt’s pretty, but how did it get there?

By Moira Whitehouse PhD

The currently accepted theory for the formation of the Moon is called the “Giant Impact” theory.

It states that about 4.5 billion

years ago, just a few

million years after

Earth had formed, a

large body (about the size of Mars)

smashed into Earth.

Due to Earth’sgravity, most of theheavier material in this cloud eventually fell back to Earth, while lighter material remained in orbit around Earth becoming the Moon.

As a result, a gusher of molten hot material was ejected into space as a cloud of debris which fell into an orbit around Earth.This debris came primarily from the Earth’s mantle.

NASA

Evidence for this idea is found in the rocks that NASA astronauts have brought back many moon rocks.

Most of these rocks were formed between 3.8 and 4.1 billion years ago.

The composition of these rocks is similar to Earth rocks.

Wikipedia commons

The diameter of the Moon is about ¼ the diameter of the Earth, butbecause it is made from lighter stuff, it is only 1/6 of Earth’s mass.

Although it looks small up there in the sky, the moon is a pretty large hunk ofrock.

Because the Moon’s mass is less , its gravity is also less than Earth’s—about one-sixth as much.Since weight depends on gravity, everything on the Moon would weigh about one-sixth as much as it does on Earth.

If this man weighed 240 lbs on Earth, he would weigh only 40 lbs on the Moon.

This boy weighs 60 pounds on Earth.

On the Moon he would only weigh 10 pounds.

Also, everything you lifted would be much lighter on the Moon that it would be on Earth. However, its mass (the amount of matter in it) would not change.

Astronaut Alan Shepard struck two golf balls with a golf club on the Moon, driving them, as he jokingly put it, "miles and miles and miles."

Because it has less gravity, astronauts made some fantastic jumps on the Moon.

Although the Moon’s gravity is less than Earths, its gravity is strong enough to affect us. Everything is pulled by the Moon’s gravity, but the only thing noticeably affected is water in the oceans. The tides occur because of this gravity’s affect on the planet. Interestingly,scientists think that it is also because of the tidal effect that the Moon is slowly drifting further away from the Earth at a current rate of 4 cm/yr.

http://kingfish.coastal.edu/marine/Animations/Tides/Tides1.html

Tidal Bulge Animation

Moon orbits the Earth

Earth orbits the Sun

Earth’s axis

It is gravity that keeps the Earth orbiting (revolving around) the Sun, the Moon orbitingthe Earth.

As interesting as gravity on the Moon is, the role gravity plays in relationship between the Sun, Earth and Moon is even more so.

NASA

As it orbits the Earth(once every 29.5 days),

(once every 29.5 days).

the Moon is also rotating on its axis,

Like the Earth the Moon rotates on its axis except much slower, once a day for Earth verses about once a month for the Moon.

Because the Moon makes one revolution in exactly the time it takes to make one orbit of the Earth, the same side of the moon always points toward the Earth.

The near side will always face toward the Earth, and the far side will always face away.

From Earth, therefore, we see only one, always the same, side of the Moon. The other side faces away from Earth and is often called the dark side of the moon.A more accurate term to describe the side of the moon we see is the near side and opposite side as the far side.

Also because the Moon is rotating (although very slowly), each side, at some point, faces the Sun and at some point, away from the Sun.

.

So the Moon has a day side and a night side, just like the Earth.But on the Moon the days and the nights last about half a month each. The parts of theMoon we can see arethe “day” parts of thenear side, the “night” parts are dark and the far side is not visible from Earth.

http://www.areavoices.com/ graphic courtesy of Bob King

To help visualize the idea that we always see the same side of the moon, imagine that you are an astronaut who was landed in the middle of the near side of the Moon and had to stay there for one month before you could be picked up.

As the Moon slowly rotates while orbiting the Earth, you remain in the center of the near side nearest Earth.

The following should interest future astronauts: Thinking about being on the Moon…

Water on the Moon?

The Moon’s structure and topography?Atmosphere on the Moon?

South pole of Moon

Scientists are not sure that there is water on the moon. Recent explorations landed a lunar probe near the Moon’s north pole looking for evidence of water. There apparently was some evidence of water in the form of ice.

Water???

The Moon has virtually no atmosphere.

Therefore, there is no weather on the Moon, no storms, no rain, no wind, no snow, but the temperature can fluxuate wildly.

The temperature on the Moon ranges from daytime highs of about 130°C = 265°F to nighttime lows of about -110°C = -170°F

Atmosphere???

The fact that the Moon has little or no atmosphere affects other things on the Moon.For example, there is no wind or water caused weathering, erosion or deposition on the Moon. Things do not erode.

http://nssdc.gsfc.nasa.gov

This footprint would look the same today as it did 30 years ago.

On the Moon, there is no air, so sound cannot travel above the surface.

The lack of atmosphere also affects sound as we know it. For sound to travel, there must be a medium for the waves to travel through.

When the Apollo astronauts were out on the Moon's surface, they could only talk to each other, and to mission control, by using the radios in their air filled helmets.

On Earth that would usually be air or water.

When the astronaut in the photo hit the moon’s surface with this shovel, no sound was made.

Even during the day time the sky looks black because the atmosphere is not there to scatter sunlight.

Another result of no atmosphere on the Moon:

The moon was formed about 4.5 billion of years ago. Most of the structures we see today, the maria and the highlands, were formed between 3.0 and 3.9 billion years ago. During that time, the Moon was bombarded by meteorites, comets and asteroids. Some of them were very large and created large impact basins.

The crust of the Moon was cracked in some places by this bombardment and magma from the interior flowed out on to the surface filling these impact basins.

Structure???

Earth was also bombarded by objects from space. However we see only a few meteorite craters because most objects burned up during entry due to friction with Earth’s atmosphere. The craters created by objects that did actually hit the surface have been eroded away by wind, rain, and other forces. There are, however, many craters on the Moon since it has no atmosphere to burn up the meteorites on entry and since there is no wind or rain to erode the impact craters away.

There is no evidence that the Moon’s crust is made up of tectonic plates. It does not seem to be tectonically active.

No volcanoes, no fold or no fault mountains are found on the Moon.

The Moon does have “moonquakes”. Almost all moonquakes are smaller than Earth’s constant grumblings and are not caused by plate movement.

Seeking information on Moonquakes, Astronaut Buzz Aldrin deploys a seismometer in the Sea of Tranquility.

There are several mountains and mountain ranges on the Moon.

Several lunar mountains are well over 10,000 feet tall.

The Moon does not have jagged mountains, instead the Moon's mountains are round and smooth.

These mountains are almost always found on the rims of large craters formed by impacts by objects in space.

http://www.areavoices.com/ photo courtesy of Bob King

Moon mountain in foreground, the Sun and planets in background.

The prominent Sculptured Hills were photographed by astronauts Schmitt and Cerman on Apollo 17. Although these hills are quite impressive, the highest mountains on the moon are 15,000 to 20,000 feet high.

The never ending bombardment of the Moon has continuously fractured and sandblasted the rock surface creating a layer of loose “soil” made up of dust and broken rock called the regolith.

The uppermost part of the regolith is mostly fine, glassy, slippery dust.

This lunar regolith covers the Moon from a depth of a few meters on the mare, to a few tens of meters on the highlands.

Astronaut Harrison Schmitt collecting rocks from the Moon during the Apollo XVII mission.

Regolith

On a clear night of moon observing, one can see that there are two types of topography on the Moon’s surface—the dark colored regions called the maria and the light-colored highlands that surround the maria.

What is it like on the Moon?

http://sos.noaa.gov/

Mare

Highlands

Photo of the near side of the Moon

They were named maria (Mare, singular), which means seas because early astronomers thought they were filled with water.

The dark material filling the Maria is actually dark, solidified lava from that earlier period of induced Lunar volcanism.

http://starchild.gsfc.nasa.gov/

They are now smooth, flat plains with little evidence of their earlier bombardment.

The flat, dark colored, smooth areas that were created appeared from Earth like “seas”.

Maria

After the earlier period of maxium maria formation, the surface of the Moon has not changed very much.There are some moonquakes which cause occasional landslides.The daily heating and cooling of rocks breaks up the rock but at a very slow rate.But the main on-going geological activity is continuing meteoritic impacts but at a much much much slower rate than in the heavy bombardment in the early history of the Moon.

Wikipedia Commons

Maria on the near side of the Moon

The highlands are hilly and heavily crateredand cover about 80% of the total lunar surface.

The far side of the Moon is made up almost entirely of highlands with many many craters and very few of the dark smooth basins called maria.

Highlands

Here we have black and white photos of both sides of the Moon.

The same photos artificially colored, give us a good idea of surface elevations on the moon.

While looking closely at the Moon, you see circles of varying circumferences, which are the craters.

There may be as many as 200,000 craters, most of them quite small, on the Moon's surface.

Most craters have a circular outline; a few are more elliptical shapes.

A crater consists of a thin elevated ring forming its perimeter.

The surface within the ring is a bit below the surrounding edge and in the center there is often a peak.

Craters range in size from a diameter of less than one mile to over 100 miles across.

The oldest basins are more irregularly shaped; the younger ones a more circular shape.

Möltke – a small bowl-shaped crater

Sabine and Ritter larger, more flattened craters

Sea of Tranquility

http://svs.gsfc.nasa.gov/vis/a000000/a003500/a003582/index.html

To open, select this one.

Phases of the Moon

2) the Moon is reflecting sunlight towards the Earth.

What causes the Moon's phases?

Half of the Moon is always in sunlight, half if it is dark: however, we can see only the lit portion which, depending on it’s position in the orbit, usually gives us a view of only part of the Moon.

The Moon goes through phases (the view seen from Earth at various times in the Moon cycle) because:

1) the Moon is revolving around the Earth,

Although it is really a continuous and gradual change, there are eight recognized phases that the moon goes through and they always occur in the same order.

In this repeating pattern the Sun's light moves, in our view, from right to left across the surface of the Moon.

The phases of the Moon are:

As shown in the diagram, the new moon occurs when the moon is positioned between the earth and sun. The entire illuminated (lit up) side of the moon is on the back part of the moon– the half that we cannot see.

http://www.wisegorilla.com free clip art for educational use

At a full moon, the earth, moon, and sun are in approximately lined up, just as the new moon, but this time the moon is on the opposite side of the earth. As a result, the entire sunlit part of the moon is facing us. The shadowed portionis entirely hidden from view.

http://www.wisegorilla.com free clip art for educational use

The first quarter and third quarter moons (both often called a "half moon"), occur when the moon is at a 90 degree angle with respect to the Earth and Sun. So we are seeing exactly half of the Moon illuminated andhalf in shadow.

http://www.wisegorilla.com free clip art for educational use

Although we give names to certain phases, each night the change is actually gradual.

http://www.valdosta.edu/~cbarnbau/astro_demos/frameset_moon.html

Select Moon Phases in the following URL for an outstanding animation of the Moon and its phases.

Select “Moon Phases”

Let’s look at the phases of the moon on a calendar for November, 2009. Notice that the change from phase to phase is very gradual and takes about a month for the cycle.

http://www.tutiempo.net/en/moon/

When a calendar month has two full moons, the second full moon is called a blue moon. (i.e. the expression once in a blue moon.)

It takes about one month, 29.5 days, for the Moon to orbit the Earth. Which, of course, is also the time from one new moon to the next.

Buddhist Proverb

Three things that cannot long be hidden: the sun, the moon and the truth.