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