Meteorites, Asteroids and Comets

1
Meteorites, Asteroids and Comets

• Solar System Debris

2
Introduction

• Meteorites, asteroids comets represent the
  unevolved remains of the solar nebula

3
Meteorites

• Meteoroids, meteors meteorites
• Mostly small particles
• Entry at 10-40km/s
• Tell us about the origin of the planets

4
Inside Meteorites

• Iron
• Iron nickel
• Widmanstatten patterns
• Remained hot for Myrs
• Stony
• Similar to Earth rocks
• Chondrites
• Carbonaceous chondrites
• Achrondrites

5
The Origin of Meteors and Meteorites

• Primordial material
• Meteor shower common origin
• ? Aquarids. 26-31 July. 15/hr
• Meteors mostly cometary debris
• Meteorites asteroidal fragments

6
Asteroids

• Mostly between Mars Jupiter
• Asteroid Belt

7
Properties of Asteroids

• Mostly km-sized or less (Ceres 30 Moon)
• Rocky, irregular, low density (1.3 kg/m3),
  craters, fragmented, double asteroids
• Near-Earth asteroids
• S (chondrite?) C(carbon) M(iron/nickel)

8
The Origin of the Asteroids

• Asteroid Belt is unformed planet
• Jupiter is to blame
• Asteroids are fragmented planetesimals

9
Comets

• Beautiful fossils of the primordial solar
  system

10
Properties of Comets

• Dirty snowballs
• Head/coma vast gas dust cloud
• Gas tail points away from Sun
• Dust tail trails along orbit

11
Comet Geology

• Subliming ices of ammonia, CO2 etc
• Giotto probe viewed small nucleus
• Dark, irregular, vents
• Density ltlt water ice implies fluffy mix of ice
  dust

12
The Origin of Comets

• Most comets are in long-period, elliptical
  tilted orbits implies a huge distant cometary
  reservoir called the Oort Cloud
• Short-period comets imply a cometary resvervoir
  beyond Neptune called the Kuiper Belt

13
Comet Impacts on Earth

• 94 comet hit Jupiter
• Dinosaur extinctioncomet or asteroid
• Impact effects
• shock wave
• tsunamis
• meteor rain
• fire storms
• darkness
• acid rain
• climate change

14
Conclusion

• Meteorites, Asteroids and Comets tell us about
  our origins here on planet Earth
• They also tell of the chances of our extinction
  due to impact
• What does this say about life on Earth and
  elsewhere?