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What’s That Up In The Sky???
The difference between
Comets, Meteors and Asteroids
Comets………Dirty Balls of Ice
They look like a star
with a ghostly white
tail.
The term "comet"
derives from the
Greek aster
kometes, which
means "long-haired
star"---a reference to
the tail.
Comets………Dirty Balls of Ice
 They can be seen by us only when they pass by the
sun and the sun’s heat melts them.
 The comet's tail is made of material from the comet;
gas from the ices and dust that is mixed in with the
ice. They escape as the comet melts.


The icy, hard part of the comet is called the nucleus.
The gas and dust are released and form an atmosphere
around the comet called the coma.
 The tail always points away from the sun due to the
solar winds (movement of heat away from sun)
Comets………Dirty Balls of Ice
 If a comet has a large orbit, it takes a
long time to go around the Sun. Some
comets are "short-period" comets that
take five or ten years to complete an
orbit. Some comets are "long-period"
comets that take decades, centuries, or
millenia to orbit the Sun.
Asteroids……Rockin’ Around
 Asteroids are
LARGE chunks
of rock and metal
that orbit the sun.
 They range from just
over ½ a mile (1km)
to a few hundred
miles in diameter
(diameter = how
wide across)
Asteroids……Rockin’ Around
 Most asteroids travel in
the wide gap between
the inner planets and
outer planets (between
Mars and Jupiter).
 But a few travel in paths
across Mar’s orbit and
some even cross in
Earth’s orbit.
Asteroids……Rockin’ Around
 Most of the chunks
or rock and metal in
space came
together long ago to
form the planets and
moons.
 Asteroids are leftover pieces of rock
from when the solar
system was formed
(“Big Bang”).
Meteors…Shooting Stars or Space
Garbage
Meteoroids
Pieces of rock or metal that travel in orbits around the sun.
Meteors
Pieces of rock/metal that are falling through the Earth’s
atmosphere from space.
Meteorites
Pieces of rock/metal that have survived the heat caused
from the friction of traveling through the atmosphere and
have HIT THE GROUND.
Meteorite composition
Major groupings:
Stony meteorites
• Chondrites
• Achondrites
Iron meteorites
Stony-iron meteorites
Chondrites
 Stony meteorites – most common meteorites
and represent the oldest solids that are the
building blocks of the solar system
 Contain up to 80% chondrules
 Chondrule-
fragments that make up the chondrite
 Subtypes:
 Breccia- VERY large chondrules
 Carbonaceous chondrites
• dark because of the materials present
Achondrites
 NO Chondrules are present because the
materials have been heated and pressurized
melting it together.
 Similar to igneous rock (colors and lines are
determined by the minerals in the meteorite).
The Johnstown Diogenite.
Lunar Meteorite Allan Hills 81005
Is there a fusion crust present?
 Fusion crust forms on entry through the
atmosphere. It looks like an outer
coating.
Identifying a meteorite
 Are there visible chondrules (large
fragments)?
 What color is the meteorite?
 Is there a fusion crust?
 Fusion
crust forms during entry into the
atmosphere. The heat melts the outside of
the meteorite forming a “crust.”
Impact Craters
Barringer Meteor Crater, Arizona, formed from Canyon Diable Meteorite
Impact Craters
 Craters formed when a meteorite
hits a solid surface on the Earth.

Size and depth will depend on the
size of the meteorite and the speed it
is falling.
 Many meteorites will break into
fragments upon impact. The type
of surface will determine how far
they scatter and how easy it is to
find the pieces.


It is easier to find meteorite fragments
in snow and sand
It is harder to find meteorite
fragments in rocky areas or grassy
fields.
Clearwater lakes, Quebec –
36+26km diameter, 290
ma
What’s That Up In The Sky???
COMETS
Made of icehave tails
Stay in space
Orbit the sun
ASTEROIDS
METEORS
Made of rock Made of rock
and metal
and metal
Stay in space Fall into
Earth’s
atmosphere
Orbit the sun Gravity pulls to
Earth; they
burn up as
they fall
What's the difference between
meteoroids, meteors, and meteorites?
Difference between:
http://www.faqs.org/faqs/astronomy/faq/p
art5/section-29.html