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Small Bodies in the Solar System
• Comets
• Asteroids
• Meteorites
What is a
• A comet is a small
body of ice, rock and
cosmic dust
• Sometimes referred to
as dirty snowballs
• The tail of a comet
occurs when solar
radiation heats the ice
and gas is given off
What is a
• The orbits of comets are
very elongated elliptical
• When a comet approaches
the sun its tail can extend
millions of kilometers
into space
• Comets often have two
tails- The ion tail, which
always points away from
the sun (because of solar
wind) and the dust tail
which can point either
Solar Wind pushes tail away from the sun
Origin of comets
• Scientists believe comets come from two
• from the Oort cloud, which is a region that
surrounds the solar system
• Also from the Kuiper belt, which is outside
the orbit of Neptune
Oort Cloud
Kuiper Belt
What are
• Large rocky
bodies (objects)
that orbit the sun,
usually found
between the
orbits of Mars
and Jupiter. This
region is called
the asteroid belt.
Types of Asteroids
• Asteroids come in many interesting shapes
and sizes
• Composition of asteroids varies usually by
where they are found
In the outermost region asteroids appear to
be rich in organic material with reddish
brown to black surfaces
Asteroids cont…
The inner most part of the asteroid belt
consists of light gray asteroids with either a
stony or metallic composition
Asteroid Belt and Meteors
Some 65 million years ago, a 10 to 12 km in size asteroid or
comet crashed on the Yucatan platform and formed the
200 km in diameter Chicxulub crater. Huge volumes of rocks
were excavated, molten and vaporized in the atmosphere in
matter of minute, altering the climate and triggering
darkness and climatic cooling as during an nuclear winter.
• When was the last asteroid strike? The last
large asteroid strike was in 1908 in Siberia
when a 60 meter stony body exploded in the
atmosphere causing a blast that knocked
over trees in an 800 mile squared area from
the blast centre. Small asteroid fragments
were found embedded in trees around the
blast site.
Artist’s depiction
• A small rocky
bodies that
revolves around
What are
the sun
Meteoroids? • Much smaller
than asteroids,
most likely they
are pieces of
names for
meteoroids to
• A meteorite is a
meteoroid that enters
Earth’s atmosphere and
strikes the ground
 A meteor is the bright
streak of light you see,
sometimes called a
shooting star
 Meteor showers are large
numbers of small
meteors usually caused
by Earth passing by
dusty debris left by a
Types of Meteorites
Three major types:
Stony iron- may contain organic materials
and water
Crater in Arizona
Impacts and the Torino Scale
• Earth is protected by its atmosphere- some
planets and moons with no atmosphere have
many impact craters
• Craters on Earth are also weathered and
• Impacts causing natural disasters are
infrequent and global impacts occur about
every 300,000 years.
What is the
The Torino scale
is a system
scientists to rate
hazard level of
an object
moving toward