The Moon Astronomy 311 Professor Lee Carkner Lecture 13

Luna -- The Goddess of the Moon Since ancient times the Moon has been thought to affect behavior (“lunatic”, “moonstruck”)

Viewing the Moon from the Earth The Moon is the nearest celestial body to the Earth and appears largest in the sky

Features of the Moon

Principle Features of the Moon Maria maria is Latin for seas Highlands Craters range in size from few hundred km to microscopic

Moon Facts Size: 3476 km diameter Orbit: 384,000 km Description: surface is similar to Mercury

The Moon’s Orbit The Moon is tidally locked The same side of the Moon always faces the Earth

Timeline of Moon Exploration Luna 1 (USSR, 1959) Luna 2 (USSR, 1959) Luna 9 (USSR, 1966) Luna 10 (USSR, 1966) Apollo 8 (USA, 1968) Apollo 11 (USA, 1969) Luna 16 (USSR), 1970)

The Apollo Program Explored the Moon from 1968 (Apollo 8 orbiter) to 1972 (Apollo 17)

Why is the Moon Airless? The Moon has no atmosphere because its gravitational pull is too weak to keep the molecules from escaping Moon may have frozen water in the permanent shadows of polar craters

The Surface of the Moon Maria: Highlands: similar to lava on Earth Highlands: Entire Moon is also covered in dust from meteor bombardment called regolith

Mare Basalt and Anorthosite

Cratering and Impacts The most common feature on the Moon’s surface are craters Every object in the solar system has been extensively bombarded in the past

Heavy Bombardment Period Early solar system had many small planetesimals and pieces of planetesimals Happened between 4.6 and 3.8 billion years ago

Forming a Crater Impactor hits surface and is vaporized Middle floor of crater often rebounds (central peak)

The Moon’s Interior Apollo missions left behind seismometers to study moonquakes Moon once had a magnetic field but does not today, indicating the presence of a small iron core that has solidified

Inside The Moon

How Did The Moon Form? What does our formation theory need to explain?

Moon Formation Theories

Collisional Ejection Theory Moon was formed when a large (Mars sized) impactor hit the young Earth The collision put large amounts of debris in orbit, which formed into the Moon

Moon Formation Impact

Moon Creation Simulation

A History of the Moon 4.6 billion years ago: 3 billion years ago-present

Summary Moon was formed 4.6 billion years ago when large impactor hit the Earth Moon has a low density because it has only a small iron core Moon has become tidally lock so that only the near-side faces Earth Most of our information about the Moon comes from the Apollo missions

Summary: Surface Maria Highlands large impacts produced basins which then filled with lava darker, denser and younger than the highlands Highlands regions that have not experienced large impacts or lava lighter, less dense and older than the maria Large numbers of impacts have covered the surface with craters and regolith (dust)