Minor Bodies of the Solar System
Moons, Asteroids, Comets, Meteoroids
Chapter 28
Satellite: A body that orbits another body (can be natural or artificial)
-6 planets have smaller bodies that orbit them
These natural satellites are called moons
Our Moon• Moon has 3 layers
– Crust• Covered in dark spots called mare
(MAHR ay)• Many craters: bowl shaped
depressions from debris impact• Regolith: layer of dust and rock• Lunar rocks- similar to rocks on earth• One side always faces away from
earth (near-side, far-side)– Pull of earths gravity makes far-side
thicker
Our Moon
• Mantle– Rock that is rich in
silica, magnesium, and iron
• Core– Small, made of iron
• Neither completely solid nor completely liquid
Formation of the Moon
• Giant Impact Hypothesis– Mars sized body struck earth
• Collision ejected chunks of earths mantle into orbit around earth to form Moon
https://www.youtube.com/watch?v=dw_Y_gujBwU
Meteorite Bombardment
• As Moon cooled it was struck with debris from formation of solar system– This produced
craters and regolith
Phases of the Moon
Phases of the Moon
Movement of the moon
• Moon orbits earth in an ellipse– Closest to Earth at Perigee– Furthest from Earth at Apogee
• Average distance from Earth is 384,000 km• Moons orbital period is 27.3 days (new moon
to new moon)• Moons rotation is same as period
• We always see same side of moon
Eclipses
Eclipse: Where one celestial body passes through the shadow of another.– Solar Eclipse: When moon is directly between the
sun and the earth. Shadow of moon is on earth
Umbra-directly in line (total eclipse)
Prenumbra- not directly in line, surrounds umbra (partial eclipse)
Eclipses
• Lunar Eclipse: When earth is between the moon and the sun. Shadow of Earth is on moon
Moon and Tides
• Tidal Bulges from Moon’s gravitational pull on earth– Regular rhythm because of earths rotation
Asteroids
Fragments of rock that orbit the sun• Sometimes called minor planets or planetoids. • Small rocky bodies floating between Mars and Jupiter• Possible extra planet that didn’t totally form
Four types of orbits: • asteroid belt• Apollo asteroids(cross Earth’s orbit) close encounters!• Amor asteroids (cross Mar’s orbit)• Trojan asteroids (inside the orbit of Jupiter).
Comets
A small body of ice, rock, and cosmic dust that follow highly elliptical orbits around the sun
• Has a core and a tail• Halley’s Comet passes earth every
76 years. Last in 1986. Next in 2061• Hale-Bopp passes every 5-10 years.
Hale-Bopp 1997
Meteoroids
• Less than 200-300 km in diameter• Most are less that 1mm• Chunks of rock & iron smaller than asteroids
orbiting the Sun. • Sizes range from grains to 100 meters across.
Meteor: Streak of light when a meteoroid enters the Earth's atmosphere and burns up. Most are tiny grains.
Meteorite: Any remnant that reaches the ground intact.
Results of Tunguska Blast, Russia Meteor Crater, AZ
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