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The Moon, Eclipses, Asteroids and Comets Notes Guide
The Moon
Moon: a body that revolves around a planet and that has less mass than the planet does.
Seven of the planets in our solar system have natural satellites, or moons. The Apollo
space program sent six spacecraft to study the moon.
The light patches seen on the moon’s surface are called _____________. The darker
areas are called _____________.
Crater: a bowl-shaped depression that forms on the surface of an object when a falling
body strikes the object’s surface or when an explosion occurs.
Lunar rocks are igneous, and most rocks near the surface are composed mainly of
____________ and _______________.
Like, Earth, the moon has three compositional layers: the _________, the __________,
and the ___________.
Formation of the Moon: The giant impact hypothesis states that the formation of the
moon began when a large object collided with Earth more than 4 billion years ago.
Eclipses
Eclipse: an event in which the shadow of one celestial body falls on another.
Solar eclipse: the passing of the moon between Earth and the sun; during a solar eclipse,
the shadow of the moon falls on Earth.
Lunar eclipse: the passing of the moon through Earth’s shadow at full moon.
Phases of the Moon
Asteroids
Asteroid: a small, rocky object that orbits the sun; most asteroids are located in a band
between the orbits of Mars and Jupiter
The orbits of asteroids are ellipses. Most asteroids are located in a region between the
orbits of mars and Jupiter known as the asteroid belt. The composition of asteroids is
similar to that of the inner planets. There are 3 types of asteroids.
The first type of asteroid is also the most common; these asteroids are made mostly of
silicate material.
The second type of asteroid is composed of mostly iron and nickel. These asteroids have
a shiny, metallic appearance, especially on fresh surfaces.
The third, and rarest, type of asteroid is made mostly of carbon materials, which give this
type of asteroid a dark color.
Comets
Comets: a small body of rock, ice, and cosmic dust that follows an elliptical orbit around
the sun and that gives off gas and dust in the form of a tail as it passes close to the sun.
The most famous comet is Halley’s Comet, which passes by Earth every 76 years. It last
passed Earth in 1986, and will return in 2061.
A comet has several parts. The core, or nucleus of a comet is made of rock, metals, and
ice. A spherical cloud of gas and dust, called the coma, surrounds the nucleus. The coma
can extend as far as 1 million kilometers from the nucleus. The nucleus and the coma
form the head of the comet. The most spectacular part of a comet is its tail. Tails form
when sunlight causes the comet’s ice to change to gas. The solar wind pushes the gas
away from the comet’s head.
Meteoroids: a relatively small, rocky body that travels through space.
Meteor: a bright streak of light that results when a meteoroid burns up in the Earth’s
atmosphere.
Meteoroids that do not burn up, but fall to Earth’s surface, are called meteorites.
There are three types of meteorites: stony, iron, and stony-iron.
Stony meteorites are similar in composition to rock on Earth.
Iron meteorites have a distinctive metallic appearance.
Stony-iron meteorites contain both iron and stone. Stony-iron meteorites are rare.