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Asteroids and Meteoroidsare they a threats to the earth?
Key words
There are eight planets in our solar system, including the Earth, and
smaller dwarf planets such as Pluto, Ceres and Eris. But there are a lot of
other objects out in space too… asteroids and meteoroids.
Asteroids and Meteoroids
What’s the Difference????
• Asteroids are large chunks of rock (but smaller than
planets) left over from the formation of the Solar System.
Asteroids come from the Leonid asteroid belt, between
Mars and Jupiter. Asteroids orbit the sun, and some
asteroids cross the Earth’s orbit. At various times during
the Earth’s history, asteroids have hit it.
• A meteoroid is a smaller chunk of rock (no bigger than a
boulder) orbiting the sun in space. They become
meteors when they fall through a planet’s atmosphere;
leaving a bright trail as they are heated by the friction of
the atmosphere (shooting stars).
• Pieces that survive the journey and hit the ground are
called meteorites.
The asteroid belt…..
• Meteorites: a portion
of a meteoroid that
survives its passage
through the
atmosphere and
impacts with the
ground without being
CC Image, Willamette Meteorite
' Courtesy of Dante Alighieri
The Willamette Meteorite on display
at the American Museum of Natural
History in New York City.
• Comets are balls of ice and dust that orbit the Sun in an
elliptical orbit, that takes it very close to the Sun, then
far away, beyond the planets.
• The time to complete an orbit can take a few years, or
millions of years.
• The speed of a comet increases as it approaches the
Sun, because the strength of gravity increases.
• Comets are often visible from Earth when they get close
to the Sun, as the ice starts to melt and forms a tail.
• Comets have been observed since ancient times and
have traditionally been considered bad omens.
The Christmas “Star of Wonder” that guided the Three
Kings was thought to be a comet…
Halley's Comet depicted on the Bayeux Tapestry which shows King Harold II
being told of the comet before the Battle of Hastings in 1066.
What happens when an asteroid
hits Earth?
When it hits.......
Huge amount of energy released
Ejection of hot rocks
Billions of tonnes of dust and hot rocks thrown into air
Smoke from widespread fires
Blocks out the heat and light from the Sun.
Changes the Earth’s climate, making it very cold.
It is thought that an asteroid colliding with the Earth
helped to drive the dinosaurs to extinction.
• Scientists worry that an asteroid could hit again and
cause a global catastrophe.
Wolfe Creek Crater
Found in 1947 in the desert plains of north-central
Australia and is thought to be about 300,000 years old and
is 880 meters across and about 60 meters deep.
Photo Credit: Dick and Pip Smith
Why do you think the surface
of the moon looks like this ?
And Earth doesn’t????
• Materials have been adapted from
resources made available on the TES
Connect website. Thanks to:
• ele89
• Mr Kelly
• funforester
• LadyAlex