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

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, commander Michael Collins, command module pilot Edwin E. Aldrin, Jr., lunar module pilot

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

The Moon’s Characteristics The surface temperature at the equator during the day is 134oC, and at night is ­­-153o C. 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

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 Regolith layer is anywhere from 3-20m thick; formed by the impact of meteors over billions of years.

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

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

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

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

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. Theory one – would require too great and atmosphere to dissipate the energy of the passing moon to capture it; also would not account for the similarity in composition. Theory two: doesn’t explain the depletion of metallic iron in the moon Theory three would require too much initial spin for the Earth None account for the high angular momentum of the Earth-Moon system.

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.