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A Solar Nebula condences to form everything but the Sun, including comets, asteroids, planets and moons.
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The inner planets (Mercury, Venus, Earth Mars) and their moons get bombarded by comets left over from planet building. These impacts are great enough to keep the planets molten.
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The dinosaurs and other creatures die out because a comet 300kms long hits Earth creating the crater called Chixculub, which is now known as Mexico's Yucatan Peninsula.
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A fifty meter wide comet hits Arozona and creats the most well preserved crater, which is 4kms long.
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The earliest record of any comet was thought to be the first sighting of the Halley's Comet
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Aristotle says that comets are in the upper atmosphere. This view lasts two-thousand years.
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Roman Emperor Costantine thought he saw a cross in the sky, so he converted his faith to christian. Some believe this was a comet, while others believe it was a meteroite impact.
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A wicked appearence of Halley's Comet is seen and then recorded on the Bayeux Tapestry before the Norman conquest of england. a piece of cloth that recorded the events before the conquest
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Tycho Brahe measures where a great comet was and compared it with other sightings, and proved it was about four times further away then the moon.
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Edmond Halley proves that comets orbit the sun by being the first to accuratly predict when a comet would reappear.
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An airburst over Siberia is heard thousands of miles away. This ear-ringing phenomena was later thought to be a comet that exploded in the outer layers of our atmosphere.
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Fred Lawrence Whipple creates a model of cometary nuclei, which still prevails. Jan Van Oort proposes that comets come from a shell of billions thousands of times further from the sun than Earth. It's now known as the Oort region.
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Geologist Eugene Shoemaker proves that aArozona was made by an impact.
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Luis Alverez and mates are the first to publish a paper linking the extintion of the dinosaurs to an impact.
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The spacewatch survey led by Tom Gehrels begins at Arizona. This is the first systematic search for any large object that might impact Earth.
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The Chixculub crater is now proven to be the cause of the extinction of the Dinosaurs.
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A US panel proposes a spaceguard program which will keep an eye on comets or metorites that are larger than one kilometer long.
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Comet Shoemaker-levy 9 discovered. Resembling a line of pearls it was most likely to be the first known comet shattered by Jupiters intence gravitational pull. In 1994 the pieces crash into Jupiter for a couple of hours.
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The Near -Earth Asteroid Tracking (NEAT) program begins at Hawaii. The rate of near asteroids increases over ten times the previous amount.
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The first asteroid that's orbit that could possibly strike Earth.
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The Tornio Scale is published by astronomer Rick Binzel. 0 = no chance 10 = almost certain global devastation.
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1950 DA is the most likely to hit Earth. It may hit Earth in 2880.
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NASA's space craft flies by a comet, collecting comet dust and taking up-close photographs. The asteroid called Apophis is rated 4 on the Torino scale - the highest ever recorded. The threat has been reduced due to improved orbital caculations. The first ever object purposly sent to impact a comet was sent on the 4th of july, and was NASA's deep impact space craft called Tempel 1. A method is proposed to move comets by using gravity.
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The US congress tells NASA to look for comets 150m wide or more, instead of over one kilometer.
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NASA's stardust spacecraft landed with examples of comet dust.
