The Moon

Objectives Describe the surface of the moon and Compare and contrast them to Earth Identify features formed by impacts Describe the Moon’s interior and how it causes the exterior J2k

Apollo Missions Apollo 1: Fire in cockpit Apollos 8, 9 & 10: Lunar orbit and return Apollo 11: Landed on Moon (Sea of Tranquility) July 20 th 1969 Apollo 12: Ocean of Storms November 1969 Apollo 13: Malfunction April 1970 Apollo 14: Fra Mauro February 1971 Apollo 15: Hadley Rille August 1971 Apollo 16: Descartes April 1972 Apollo 17: Taurus-Littrow December 1972

Surface Features Dark areas are smooth (fewer craters) Called maria Basalt More dense Younger Light area more craters Called highlands Anorthosite Less dense Older

Rays and Rilles Rays – Radiate outward from many craters – Pulverized rock Rilles – Lunar canyons – Crustal cracking

Formation of Craters, Rays, Maria and Rilles Rays – Vaporized rocks expand outward – Some rebounded asteroids will cause a peak to form Marias – Also impact features – Molten early moon – Molten material from inside the moon leak to the surface

Structure of the Moon Moon cools more than Earth…why? Regolith – Blanket of rock – Rock chunks and fine powder Crust & Interior – Moon is less dense than Earth (3.3 vs 5.5 g/cm3 Less iron – Moon has no magnetic core Little molten rock – Crust is thinner on near side of moon – Far side is heavily cratered with little to no Maria

Moon’s Atmosphere Almost no gas (He) – Interior too cool = no volcanic activity – Gravity too weak No atmosphere = – Large temp fluctuations – No wind

On the “hoax” 908

Distance to the Moon Approximately 250,000 miles Reflectors – Placed by astronauts – Accurate to the cm

Synchronous Orbit Rotation same as it’s orbit Common with most satellites

Unique Qualities Tilted orbit – Neptune’s moon Triton has the most off center orbit Size relative to Earth – Suggest that our moon formed differently

How did our moon form? Before Apollo missions – Small planet captured by Earth’s gravity (capture theory) – Moon and Earth were “twins” forming side by side from a common cloud of dust (twin formation theory) – The Earth initially spun faster and formed bulge that “broke” away (fission theory)

Current Hypothesis Violent Birth – Mars sized body collides with Earth – Debris forms the moon Low iron content due to crust of Earth

Tides Moon’s gravity causes a tidal “bulge” on side with moon and the opposite side As Earth rotates it passes through two bulges = 2 high tides and 2 low tides/day Especially high tides during full and new moon…why? – Sun is adding its gravity narcycles/tidesim.html

Tidal Braking Moon’s gravity pull bulge backward, slowing the rotation of the Earth (.002 seconds each century) Also causes synchronous orbit of moons