2.  A natural satellite  The only moon of the planet Earth  One of more than 96 moons in our Solar System

3.  About 384,000 km (240,000 miles) from Earth  Earth’s radius = 6378 km or 3963 miles  Moon’s radius = 1738 km or 1080 miles  About ¼ size of Earth

4.  If earth were a basketball, then the moon would be a tennis ball 23.5 feet away

5.  “Born” 4-5 billion years ago  Formed from impact of Mars-sized “planetesimal” on Earth  Debris from both objects melted together to form the moon

6.  No atmosphere  No liquid water  1/6 Earth’s gravity  Because the moon has less mass than the earth does (1/80 of earth), its gravity is weaker  Extreme temperatures  Daytime 130 o C (265 o F)  Nighttime -190 o C (-310 o F)

7.  Maria  Rilles  Craters  Highlands  Lunar Rocks

8.  Highlands – mountains up to 7500 meters (25,000 feet) tall  Rilles – trenchlike valleys that look somewhat like a dry riverbed. Were probably lava channels when the moon was volcanically active. Some as long as 240 km.

9.  Originally thought to be “seas” by early astronomers  Darkest parts of lunar landscape  Filled by lava after crash of huge meteorites on lunar surface 3-4 billion years ago  Mostly basalt rock

10.  Up to 2500 km (1,553 miles) across  Most formed by meteorite impact on the Moon  Some formed by volcanic action inside the Moon

11.  The oldest moon rock is 4.3 billion years old  Moon rocks contain many of the same elements that occur in the earth’s rocks, but in slightly different proportions  Moon surface rocks are deficient in elements with low melting points, such as sodium  Minerals in moon rocks do not contain water  Surface rocks on the moon are about as dense as those on the surface of the earth

12.  Crust – average thickness of about 70 km  Mantle  Made up of dense rock that is probably rich in silica, magnesium, and iron  Reaches to a depth of about 1,000 km  Core – radius is between 300 and 425 km

13.  First seen by Luna 3 Russian space probe in 1959  Surface features different from near side  More craters  Very few maria  Thicker crust

15.  Orbit of moon around the earth forms an ellipse, not a circle  The moon rises and sets 50 minutes later each night  Moon rises in the east and sets in the west  Revolution – Moon orbits the Earth every 27 1/3 days  Rotation – Moon turns on its axis every 27 days  Same side of moon always faces Earth  Observers on Earth can see about 59% of surface of moon

16.  When the moon is between the Earth and the Sun  Moon casts a shadow on part of the Earth  Total solar eclipses are rare – only once every 360 years from one location on Earth

17.  Occurs when the Earth is positioned between the moon and the sun, and the Earth’s shadow crosses the lighted half of the moon  This shadow darkens the moon  About 2-3 per year  Lasts up to 4 hours

18.  Moonlight is reflected sunlight  Half the moon’s surface is always reflecting light  From Earth we see different amounts of the Moon’s lit surface  The amount seen is called a “phase”

19. FULL CRESCENT QUARTER GIBBOUS

20.  New moon  Waxing Crescent moon  First Quarter moon  Waxing Gibbous moon  Full moon  Waning Gibbous moon  Third Quarter moon  Waning Crescent moon  New moon

22.  Tides caused by pull of Moon’s gravity on Earth  High tide –  Side facing Moon and side away from Moon  Every 12 hours, 25 ½ minutes  Low tide –  On sides of Earth

23.  1950s to 1960s - probes  Neil Armstrong First man on the Moon – July 20, 1969  Six Apollo missions (1969-1972)  382 kg (842 lbs) rocks  12 Americans have walked on the moon

24.  The 3 basic units of most calendars – day, month, and year – are determined by the movements of the earth and the moon  Day – time required for the earth to make one rotation on its axis (about 24 hours)  Month – time required for the moon to go through one cycle of phases as it orbits the earth (29.5 days)  Year – time required for the earth to make one orbit around the sun (about 365.24 days)

25.  All planets except Mercury and Venus have moons  In addition, Saturn, Jupiter, Uranus, and Neptune have rings  Mars has 2 moons (Phobos and Deimos) that revolve around Mars quite rapidly  Jupiter has at least 17 moons and most are very small. The 4 largest satellites of Jupiter are called Galilean Moons because they were first seen by Galileo in 1610  Saturn has at least 18 moons. Most are small, icy bodies with many craters  Uranus has at least 20 small moons  Neptune has 8 known moons (Triton and Nereid are among the 8)  Pluto has 1 moon, Charon, that was discovered in 1978