The Moon Chapter 10

The Earth Moon System

Primary Surface Features

The moon is really not very far away at all….. Additionally, the moon has a very low escape velocity, which, combined with it’s rather warm temperature (in sunlight) of about 130 oC, permitted all gases to escape. Consequently, the Moon has no atmosphere.

Clavius Crater (diameter = 144 miles, 16,000ft deep)

Studying craters within craters allows scientists to build up a “cratering record”; a record of the number of impacts as a function of time. There is no weathering on the moon, so the moon’s surface retains a permanent record of the era of bombardment that followed the formation of the planets.

Mare Tranquilitatis - Apollo 11 Landing Site

Whilst there is evidence for Lava flows on the moon, there never were any volcanoes! The idea that there were volcanoes on the moon is a common misconception!

Large impacts, caused by the same group of comets that delivered water to the Earth, penetrated the thin lunar crust allowing the molten mantle (ie. lava) to emerge onto the lunar surface, resulting in maria

Mare Imbrium (diameter = 700 miles)

Another curious feature of the moon is that the near side and far sides are quite different, - the moon is asymmetric.

Moon Near and Far Sides

Iron content measured by Clementine

The Moons Interior

Like the Earth, the Moon has a core, mantle and crust Like the Earth, the Moon has a core, mantle and crust. Unlike the Earth, the Moon does not have plates, so there is no plate tectonics on the Moon. The Moons surface has remained unchanged since it formed 4.5 billion years ago, modified only by impacts.

The moon is, of course, the only celestial object that humans have ventured to, off the Earth. There were a total of 6 lunar landings, Apollo 11, 12, 14, 15, 16 and 17. Apollo 11, the first lunar landing, occurred on July 20, 1969, and Neil Armstrong was the first man to step on the moon, closely followed by Buzz Aldrin. They spent about 21/2 hours on the lunar surface and the Lunar module was on the moon for less than 24 hours.

Apollo 11

Apollo 12

Apollo 15

Lunar Regolith

Mare Basalt

The Apollo astronauts collectively returned nearly 1,000 lbs of lunar rocks! All of the lunar rocks are igneous, there are no sedimentary or metamorphic rocks.

Anorthosite - Highlands rock

Impact Breccias

A continuing puzzle is where the moon came from. There are 3 contending theories: The most popular is the “collision theory” The least likely is the “capture theory” less likely is the “Fission theory” What confuses the issue is that the chemical composition of the Moon is quite different from the Earths.

Collision Theory for the Origin of the Moon

Are Lunar Bases likely in the future? Well, the moon does not have a lot going for it as far as offering good prospects for human habitation. It has no atmosphere, no water, and no magnetic field to offer protection from damaging cosmic radiation.