Download Space Wk 6 Student PPT

Meteors
• A streak of light ( a “shooting star”0 that
suddenly appears in the sky when a particle
from a comet or asteroid enters the Earth’s
atmosphere
• Most meteors occur in the region of the
atmosphere called the thermosphere. This
“meteoric region” lies between about 80 km
and 120 Km in altitude.
Meteor Terminology
• Comet—a solid body made of ice, rock, dust, and
frozen gases. As they fracture and disintegrate,
some comets leave a trail of solid debris
• Asteroid---amall rocky, iron, or icy debris flying in
space
• Meteoroid---a small asteroid
• Meeor Shower---an annual event, when Earth
passes through a region having a great
concentration of debris, such as particles left by a
comet. From Earth, it looks like meteors radiate
from the same point in the night sky.
Meteor Terminology
• Meteor---the light emitted from a meteoroid or
an asteroid as it enters the atmosphere
• Fireball—a meteor brighter than the planet Venus
• Bolide---the light emitted by a large meteoroid or
an asteroid as it explodes in the atmosphere
• Meteorite---a fragment of a meteoroid or an
asteroid that survives passage through the
atmosphere and hits the ground
Meteorite
• A fragment of a comet or asteroid that
survives its passage through the Earth’s
atmosphere and lands on the Earth’s surface
• The Barringer Meteorite Crater in Arizona,
about 0.6 miles across, is only 50,000 years
old and so well preserved that it has been
used to study impact process
Meteorite
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Three types
-----Iron
-----Stony
------Stony-iron composition
• Most meteorites formed 4.55 billion years ago
• November 30 1954—Ann Hodges is severely bruised by
an 8 lb. stony meteorite when it crashes through her
roof in Sylacauga, Alabama. ( The only person to have
ever been injured by a meteorite.)
Meteorite
• Meteorites may resemble Earth rocks, but they
usually have a burned exterior. This fusion crust is
formed as the meteorite is melted by friction as it
passes through the atmosphere.
• Majority of meteorites that fall are irons- these
heavy objects are easier to distinguish from Earth
rocks than stony meteorites.
• More than 50,000 meteorites found on Earth99.8% come from asteroids
Asteroids
• small, rocky solar system bodies that populate
interplanetary space out to the orbit of Jupiter.
• Millions—often grouped by composition
• Refered to by scientist as minor planets
• Minor planets—solar system bodies smaller that
moons
• Mainly made of materials left over from the
formation of the inner solar system worlds
Asteroids
• Most orbit Sun between Mars and Jupiter (Asteroid Belt)
• Three Composition classes
• ------------C-types (chondrites)—made of clay and silicate
rocks
• -------------S-types---stony asteroids and are made mostly
of silicate rocks and nickel-iron mixtures
• --------------M-types—metalic nickel-iron
• These categories indicate how far from the Sun they
formed in the early solar system.