Meteors and Meteorites

1
Meteors and Meteorites
2
So what are Meteoroids? Meteors? Meteorites?

• Small pieces of space debris (usually parts of
  comets or asteroids) that are on a collision
  course with the Earth are called meteoroids.
• When meteoroids enter the Earth's atmosphere they
  are called meteors.
• If the meteors survive and strike the surface of
  the Earth they are called meteorites.

3

• Barringer Crater in Arizona

It is 1.2 kilometers across and 200 meters deep,
and was formed about 49,000 years ago by the
impact of a 50 meter nickel/iron meteorite
traveling at a speed of 11 kilometers per second.

4
Meteors - Shooting Stars

• Most meteoroids are tens of meters in diameter or
  less.
• Enter Earths atmosphere and become meteors or
  shooting stars.
• Most meteors are tiny specks of dust.
• Larger meteors produce fireballs.

5
Meteor Showers and Comets

• Occur on a regular schedule

6

• What are meteor showers???
• - result when the Earth encounters cometary
  orbits
• The annual nature of meteor showers hints to the
  nature of the orbits of meteoroids.

7

• Several hundred tons of meteoroids enter the
  Earth's atmosphere each day. Most of these are
  very small pieces (milligrams) that burn up
  quickly in the atmosphere and never reach the
  surface.

8

• The track of the meteoroid in this image is only
  about 0.05 inches long. The meteoroid itself has
  a diameter of only about 1/1000 of an inch!!!!

9
Chondrite (Stony) Meteorites

• By far the largest number of meteorites fall
  into this class similar in composition to the
  mantles and crusts of the terrestrial planets

10
Iron Meteorites

• primarily iron and nickel

11
Carbonaceous Chondrites

• May contain organic compounds that may hold keys
  to how life developed in the Solar System.

12
Meteorite ALH84001
13

• Discovered in Antarctica
• Dislodged from Mars about 16 million years ago
• Fell to Earth 13,000 years ago
• May contain fossil evidence that may indicate
  that primitive life existed on Mars more than 3.6
  billion years ago.

14
The Asteroid and the Dinosaur

• It has been proposed that 65 million years ago
  in what is now Yucatan the impact at a velocity
  of 11 km/second of a 10-kilometer wide asteroid
  threw huge amounts of matter into the atmosphere
  (in addition to local phenomena like generating
  2000 foot waves that may have emptied the Gulf of
  Mexico!). This created months of darkness
  (interfering with photosynthesis) and much cooler
  temperatures globally, and the resulting harsh
  conditions led to the extinction of many species,
  including the last of the dinosaurs.