Download Metallic meteorites

Ch. 16-5 Small Bodies in
the Solar System
Pages 500 - 505
COMETS
*A comet is a small body of ice, rock, and cosmic
dust loosely packed together. “Dirty Snowballs”
Nucleus -the
solid center.
Dust tail - gas and
dust when ice melts
from the sun’s heat.
Ion tail electrically
charged
particles
from solar
wind.
Comet Shoemaker Levy
July 1994
Impact with Jupiter
Where Do Comets Come From?
*Many scientists think they come from a
spherical region called the Oort cloud that
surrounds the solar system. The gravity of a
passing planet or star disturbs part of this
cloud and comets are pulled in toward the sun.
ASTEROIDS
*Asteroids are small, rocky bodies in
orbit around the sun. They can be a
few meters to nearly 1000 km in
diameter.
Where do Asteroids Come From?
* From the
asteroid belt
which is a wide
region
between the
orbits of Mars
and Jupiter.
METEOROIDS
* A meteoroid is a
small (much smaller
than asteroids), rocky
body orbiting the sun..
* If a meteoroid
enters the earth’s
atmosphere and strikes
the ground it is called a
meteorite.
SHOOTING STARS
(are not stars at all!)
*The bright streak
of light caused by a
meteoroid or comet
dust burning up in
the atmosphere is
called a meteor.
Composition of Meteorites
Stony meteorites are similar to the composition
of rocks you would find on Earth.
Metallic meteorites are made of mostly
metals.
Stony-metallic meteorites, the third
type, contain iron and stone.
Why does the moon have so
many impact craters?
*The Earth has an
atmosphere which acts like a
shield in which small bodies
burn up before they reach
the surface.
*The moon has no atmosphere
to protect it. Also, there is
no weathering on the moon to
erase the craters.
Impacts on Earth
• Most objects that come close to Earth are small and usually
burn up in the atmosphere.
• About 65 million years ago, a meteor 10 km wide struck
Earth and caused 15-20% of all species, including the
dinosaurs, to become extinct.
Meteor Crater
Arizona
• Most craters on the Earth are hidden by erosion, plants or
the oceans.