comets and impact crators
DESCRIPTION
COMETS AND IMPACT CRATORS. Mullard Space Science Laboratory University College London http://www.mssl.ucl.ac.uk. What is a Comet ?. Comets are small, fragile, irregularly shaped bodies composed mostly of a mixture of water ice, dust and carbon- and silicon-based compounds. - PowerPoint PPT PresentationTRANSCRIPT
06/08/03
COMETS ANDIMPACT CRATORS
Mullard Space Science Laboratory
University College London
http://www.mssl.ucl.ac.uk
06/08/03
What is a Comet ?
Comets are small, fragile, irregularly shaped bodies composed mostly of a mixture of water ice, dust and carbon- and silicon-
based compounds.
Comets have highly elliptical orbits thatrepeatedly bring them close to the Sun
and then swing them into Space.
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Parts of a Comet
Hydrogen Cloud Ion Tail
Nucleus
ComaDust Tail
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Ingredients for the Nucleus of a Comet
1. Water
2. Ammonia
3. Sand or Fine-grained Dirt
4. Salt
5. Methane
6. Crushed Charcoal briquettes
7. Organic compounds
8. Alcohol
9. Dry Ice
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Shoemaker-Levy 9Collision with Jupiter
Date: July 16th – July 22nd 1994Diameter: 20 fragments up to 2 km
The large dark “scars” seen on the above imagewere the result of the impact of fragment G
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Tunguska Comet Impact
Area : Earth, Siberia, TunguskaDate : 7.17AM, June 30th, 1908
A mysterious explosion occurred in the skies over Siberia. This explosion was caused by the
impact and breakup of a large meteorite, at an Altitude of roughly 6km in the atmosphere.
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Chicxulub Impact Crater
Area : Earth, Mexico, Yucatan PeninsulaAge : 65 million yearsDiameter : 170 km
Thought to be the cause of the extinction of the dinosaurs !
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How is an Impact Crater Formed ?
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Two Types of Impact Crater
1) Simple Crater – Bowl-shaped, smooth-walled craters of a small size.
2) Complex Crater – Larger craters that can collapse,form terraces, central peaks, central pits, multiple rings and peak ring basins.
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Making an Impact Crater
1. Fill a pan with surface material (flour) to a depth of about 2.5cm.
2. Smooth the surface, then tap the pan to make the material settle evenly.
3. Sprinkle a fine layer of coloured material (dry paint, or powdered drink mix), evenly and completely over the surface. (Use a sieve or sifter for more uniform layering).
4. Then sprinkle a fine layer of sand or flour over the top.
5. Use different side balls and drop from different heights, and observe the impact craters produced.
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Barringer Meter Crater
Area : Earth, ArizonaAge : 49,000 yearsDiameter : 1.186 km
Simple meteorite impact crater
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Wolfe Creek Crater
Area : Earth, AustraliaAge : 300,000 yearsDiameter : 0.875 km
Simple impact crater
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Aorounga Crater
Area : Earth, ChadAge: 200 million yearsDiameter : 17 km
A buried complex crater with dark streams
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Bessel Crater
Area : MoonDiameter : 16 km
In between a simple and complex crater
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Copernicus Crater
Area : MoonAge: > 1 billion yearsDiameter : 93 km
Complex crater with central peak and rays
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Yuty Crater
Area : Mars, North HemisphereDiameter : 10 km
Complex crater with central peak and fluid flow
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Meitner Crater
Area : VenusDiameter : 150 km
3rd Largest impact feature on Venus with 2 circular rings
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What is a Meteor, a Meteoroid, a meteorite,
and an Asteroid.
• Meteor - a flash of light in the night sky due to the friction of a meteoroid passing through the atmosphere.
• Meteoroid - an interplanetary chunk of matter smaller than 1km and frequently millimeters in size.
• Meteorite – an part of a Meteoroid that survives the fall through the atmosphere and lands on the Earth.
• Asteroid – a larger chunk of rock that comes from the asteroid belt located between the orbits of Mars and Jupiter.