1. Minor members of the Solar System Asteroids, Meteors, Comets

2. Formation We have already seen how the solar system formed Some planetesimals were left over when the solar system formed These became the asteroids, meteoroids and comets Many of the asteroids are in the asteroid belt. What is an asteroid belt like?LinkLink

3. The Asteroid Belt The asteroid belt occurs in orbit between Mars and Jupiter The combined left over mass was not quite large enough to form another planet, especially due to the large disruptive force of gravity from nearby Jupiter, with its great mass. Had the left over mass been larger, we might have had another planet there

4. Asteroids So, asteroids are remnants from the formation of the solar system They are therefore 4.5 billion years old and when we find pieces of them they give us information about the origins of the solar system That is why we send probes to comets and asteroids Ida and Dactyl Eros

5. Asteroids Asteroids occur in 3 types –Stony –Iron –Stony-iron These actually are parts of asteroids that differentiated as shown in the link below

6. Meteoroids, meteors, meteorites These are actually all the same thing They are named differently depending on their location Small asteroid pieces are meteoroids When they fall towards earth, burning up, they are called meteors. We get some of these all the time If they actually hit the surface, then they are meteorites Leonid Meteor

7. Comets Comets are icy remnants of the solar system, with a small hard nucleus core and the surrounding gaseous coma They reside in two regions, the Oort cloud and the Kuiper Belt They orbit the sun in long period elliptical orbits They begin to heat and vaporize as they approach the sun, forming a tail. The tail always points away from the sun, being pushed there by solar wind and radiation pressure Hale-Bopp

8. Meteor showers Many comets are periodic, visiting the sun regularly When comets go around the sun, they leave many small pieces in their orbital paths When the earth intersects this comet debris, we get meteor showers – many small meteors giving us a great light show as they burn up – rarely touching the ground We can predict when we get these since we cross these orbital paths periodically, like the Perseids every August The complete breakup of comet Shoemaker-Levy 9 in 1994 produced this spectacular telescopic image below After colliding with Jupiter

9. Collisions This is worrisome since the earth periodically also gets hit by larger solar system remnants – asteroids or comets The mass extinction at the end of the Mesozoic was probably due to an impact in the Yucatan There is a small government program that searches for asteroids on collision paths with earth. If a large one hits, it would be very bad for us

10. Review How old are asteroids Where are most asteroids located Where do you find a meteorite? Where are comets located? Which way does the tail of a comet point? Why do metoer showers occur?

11. How likely is a large collision? The map below shows major impact sites around the world. There are many of them.

12. Craters Most craters have been weathered and are not visible anymore But they give evidence that we have been visited many times by these fragments from space And it has happened before What if a collision sent new asteroids our way. Could this happen?

13. The End?