section+1+-+Background+information

__ //**Section 1 Background information** // __ ** __Evidence for impacts with Earth in the past__ A 10 kilometer across rock collided with Earth. This is the size of the comet believed to have hit Earth 65 million years ago, killing off the dinosaurs and two-thirds of all life.

On Earth, however, processes of resurfacing and erosion have covered up many craters. Tectonic activity- particularly volcanoes – has deposited layers of rock on top of craters. Other impact sites have been covered by the action of wind and water.

Some impact craters are still clearly seen. Among the best are Meteor Crater in Arizona, USA and Wolf Creek in Australia. Now others like Manicouagan in Canada are being identified by satellite images.

This Crater called Chicxulub may be the site of the meteorite impact some 65 million years ago which wiped out dinosaurs**.

**One traveled north up the east coast of the USA, giving a firework trail seen by millions.
 * __ Recent impacts events __**

One piece survived and crashed down in Peekskill, New York-on Michelle Knapp’s 1980 Chevrolet

A car honking space rock struck in Spain on June 21, 1994

Around midnight on February 18, 1995 many people in Japan saw a bright fireball cross the sky.

On September 29, 1938 a 1.8kg stone fell on a Pontiac coupe in Illinois, USA.

On the evening of October 9 1992 thousands of Americans saw a fireball brighter than the full moon fall across the sky.

Most of the asteroid burned up in its fall through the atmosphere, but a 12kg fragment survived to crash on a car in Peekskill, New York.**

Meteors are shooting stars ****, **** if a meteor reaches the ground and survive impact, and then it is called a meteorite. ** Comets are huge lumps of dirty ice, mixed with dust and grit ** The orbit of the original asteroi ****d: ** Orbital time: 1.82 years Inclination of Orbit: 5 degrees Eccentricity: 0.41 ** Comets come from the Kuiper Belt and the Oort ****’s **** cloud. ** Blocks of ice formed in the cold outer regions beyond the planets ****, some of these ice blocks were gobbled up by the gas giant planet. ** The asteroids are rocks left over from before the birth of the planets some 4.5 billion years ago. The gravitational pull of nearly Jupiter stopped them coming together and making a planet. ** 65 million years ago it is thought that a comet struck the Earth ****, **** It threw billions of tones of dirt into the atmosphere and changed climate ****, **** Comets could also be key life on Earth ****, their ****Ice could ****account for much of ****the water in the oceans ****<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';">, ****<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';">Organic molecules trapped in ice could have been ingredients for starting life ****<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';">. **
 * __ The nature of impact objects,What they are,where they come from __**
 * <span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';">Asteroids ****<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';"> are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are smaller than planets but larger than meteoroids. **<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';">Meteoroid ****<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';"> is a particle of debris in the Solar System ****<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';">. **<span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';"> **
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 * <span style="color: #ff99cc; font-family: 'Arial Rounded MT Bold','sans-serif';">Average distance from the Sun: 225, 000, 000km
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