The Earth and Its Moon

1. The Earth and Its Moon Part 2: The Earth’s Moon

2. Men on the Moon • The Apollo space program’s objective was to land men on the moon and bring them safely back home. • 1st moon landing was July 20, 1969 in the Sea of Tranquility • From 1969 through 1972, 12 men from 6 missions walked on the moon. Neil A. Armstrong, commanderMichael Collins, command module pilotEdwin E. Aldrin, Jr., lunar module pilot

3. The Moon’s Characteristics • Diameter: 3476km (about ¼ Earth’s) • Mass: about 1/80th that of the Earth • Gravity: about 1/6th that of Earth • Average Distance from Earth: 363,301km Comparative sizes of the Earth and the Moon, as imaged by Deep Impact in September 2008 from 50 million km away. Credit: NASA Moon Facts: http://lro.gsfc.nasa.gov/moonfacts.html

4. The Moon’s Characteristics • The surface temperature at the equator during the day is 134oC, and at night is ­­-153oC. • The moon is not round, but egg shaped with the large end pointed towards earth.  • The moon has no significant atmosphere or clouds. Full Moon photograph taken from Madison, Alabama Photo Credit: Gregory H. Revera

5. The Moon’s Structure • Similar to Earth’s • Iron-rich inner core with a radius of nearly 150 miles • Fluid, primarily liquid-iron, outer core • A partially molten boundary layer around the core • Mantle • Crust – 60 km thick • Regolith: layer of dust, soil, and broken rock covering most of the moon

6. Features of the Moon • Highlands: mountain ranges • Maria (MAHR-ee-uh; singular-mare; Latin for seas): broad, smooth, lowland plains; the dark areas; vast solidified pools of ancient basaltic lava; evidence that the moon was once hot and active Near side (left) and far side (right) of the Moon, by Lunar Reconnaissance Orbiter

7. Features of the Moon • Rilles: long valleys • Craters: primarily impact craters formed by the continuous bombardment of the moon by meteorites • Estimated to be about 300,000 larger than 1km across • Named for scholars, scientists, artists and explorers; Copernicus is an example Near side (left) and far side (right) of the Moon, by Lunar Reconnaissance Orbiter

8. Movements of the Moon • The Moon's orbit is inclined about 5 degrees from the Earth's ecliptic orbit around the sun. • One revolution takes about 27.3 days.(The Orbital speed of the moon is 3,680 km/h.) • One rotation of the moon on its axis takes about the same 27.3 days. • Because a revolution and a rotation take the same time, we always see the same side of the moon. http://myscientificbluff.blogspot.com/2009/03/why-moon-rises-50-minutes-later.html

9. Movements of the Moon • The orbit of the moon is elliptical. • Perigee: point closest to Earth; about 362,600 km • Apogee: point farthest from Earth; about 405,400km

10. Origin of the Moon • The moon is about 4.5 billions years old Formation: • One Theory: The moon formed far away from the Earth and was then “captured” by the Earth’s gravity. • Second Theory: The moon formed along with the Earth. • Third Theory: The moon split off from the Earth due to centrifugal force. • Each of these theories fails in some way to account for all the evidence we have.

11. Origin of the Moon • Current Prevailing Theory: Soon after the Earth was formed, a Mars-sized asteroid impacted it and blasted material into orbit around the Earth. That material came together to form the moon. • Recent evidence (2012) suggests that this may not be correct, as the moon’s composition appears to be exactly the same as the Earth’s, with no second contributor.