Comets, Asteroids, Comets, Asteroids, Meteoroid and MeteoritesMeteoroid and Meteorites

Chapter 21 Section 5Chapter 21 Section 5

Pages 668-673Pages 668-673

CometsCometsA comet is a small body of ice, rock and A comet is a small body of ice, rock and cosmic dust loosely packed together.cosmic dust loosely packed together.

Scientists refer to them as dirty Scientists refer to them as dirty snowballs.snowballs.

Comet’s OrbitComet’s OrbitComets orbit the Sun in highly elliptical orbitsComets orbit the Sun in highly elliptical orbits.. Their Their velocity increasesvelocity increases greatly greatly when they are near the when they are near the Sun and slows down at the far reaches of the orbit. Sun and slows down at the far reaches of the orbit. Since the comet is light only when it is near the Sun (and Since the comet is light only when it is near the Sun (and is it vaporizing), is it vaporizing), comets are darkcomets are dark (virtually invisible) (virtually invisible) throughout most of their orbit.throughout most of their orbit. The The solar wind pushes the tail away from the Sun. solar wind pushes the tail away from the Sun.

Parts of a CometParts of a CometWhen they are near the When they are near the Sun and active, comets have and active, comets have several distinct parts: several distinct parts: Nucleus:Nucleus: relatively solid and stable, relatively solid and stable, mostly ice and gasmostly ice and gas with a small amount of dust and other solids; with a small amount of dust and other solids; Coma:Coma: dense cloud of water, carbon dioxide and otherdense cloud of water, carbon dioxide and other neutral gases neutral gases Hydrogen cloud:Hydrogen cloud: huge (millions of km in diameter) but huge (millions of km in diameter) but very sparse very sparse envelope of neutral hydrogenenvelope of neutral hydrogen; ; Dust tailDust tail:: up to 10 million km long composed of smoke-up to 10 million km long composed of smoke-sized dust particlessized dust particles driven off the nucleus by escaping driven off the nucleus by escaping gases; this is the most prominent part of a comet to the gases; this is the most prominent part of a comet to the unaided eye; unaided eye; Ion tailIon tail:: as much as as much as several hundred million km longseveral hundred million km long composed of plasma and laced with rays and streamers composed of plasma and laced with rays and streamers caused by interactions with the caused by interactions with the solar wind. .

The comet's tail gets bigger as it gets closer to the sun and then decreases as it moves away from the sun.

Comets FactsComets FactsA comets A comets ion tail always points away from the ion tail always points away from the sun.sun.

Solar winds blow the ion tail away from the Solar winds blow the ion tail away from the sun.sun.

The The dust tail follows the comet’s orbit and do dust tail follows the comet’s orbit and do not always point away from the sun.not always point away from the sun.

Scientists believe that Scientists believe that comets come from the comets come from the Oort Cloud, a region that surrounds the solar Oort Cloud, a region that surrounds the solar system.system.

Comets Comets can also come from the Kuiper Belt can also come from the Kuiper Belt which exists outside of Neptune’s orbit.which exists outside of Neptune’s orbit.

Shoemaker-Levy CometShoemaker-Levy Comet

On 1994 July 16-22, over twenty fragments of On 1994 July 16-22, over twenty fragments of comet Shoemaker-Levy 9 collided with the comet Shoemaker-Levy 9 collided with the planet Jupiter. planet Jupiter.

The comet, discovered the previous year by The comet, discovered the previous year by astronomers Carolyn and Eugene Shoemaker astronomers Carolyn and Eugene Shoemaker and David Levy, was observed by astronomers and David Levy, was observed by astronomers at hundreds of observatories around the world at hundreds of observatories around the world as it crashed into Jupiter's southern hemisphere. as it crashed into Jupiter's southern hemisphere.

Video Link to NEO’s Video Link to NEO’s (Near Earth Objects)(Near Earth Objects)

http://neo.jpl.nasa.gov/neo/

AsteroidsAsteroids

Asteroids are Asteroids are small rocky bodies that revolve small rocky bodies that revolve around the sun.around the sun.They They range in size from a few meters to more range in size from a few meters to more than 900 kilometers in diameterthan 900 kilometers in diameter..Asteroids Asteroids have irregular shapes, but some are have irregular shapes, but some are spherical, or roundspherical, or round..Most asteroids Most asteroids orbit the sun in asteroid belt.orbit the sun in asteroid belt.The The asteroid belt orbits between Mars and asteroid belt orbits between Mars and Jupiter.Jupiter.Asteroids are Asteroids are thought to be left over from the thought to be left over from the formation of the solar system.formation of the solar system.

Meteoroids, Meteors and Meteoroids, Meteors and MeteoritesMeteorites

Meteoroids are small rocky bodies that Meteoroids are small rocky bodies that travel through spacetravel through space. .

A meteor is a bright streak that results A meteor is a bright streak that results from a meteoroid burns up in Earth’s from a meteoroid burns up in Earth’s atmosphere, what we call shooting stars.atmosphere, what we call shooting stars.

A meteorite is a meteoroid that reaches A meteorite is a meteoroid that reaches the Earth’s surface without burning up.the Earth’s surface without burning up.

Three Types of MeteoritesThree Types of Meteorites

Stony- Rocky materialStony- Rocky material

Metallic- Iron and NickelMetallic- Iron and Nickel

Stony Metallic- Rocky material, iron and Stony Metallic- Rocky material, iron and nickelnickel

Stony MeteoritesStony MeteoritesRocky materialRocky material

Metallic MeteoriteMetallic Meteorite

iron and nickeliron and nickel

Stony-Iron MeteoriteStony-Iron Meteorite

rocky material, iron and nickelrocky material, iron and nickel

Meteorite Crater-Winslow, ArizonaMeteorite Crater-Winslow, Arizona

Winslow, Arizona Winslow, Arizona

This crater was formed approximately 50,000 years ago when an iron mass, estimated to be about 80 feet in diameter and weighing over 60,000 tons entered the Earth's atmosphere over the American Southwest. The resulting formation is about 4,000 feet (1,200 meters) wide and 570 feet (175 meters) deep.

A fragment of the meteorite that A fragment of the meteorite that created Meteorite Crater.created Meteorite Crater.

Metallic Meteorite