EAS206 Lecture Notes - Lecture 15: Impact Crater, Chondrite, Meteoroid
Meteorites
• Meteoroid
o Slows and fragments
▪ Friction
• Heats outside, light
• Meteor
o Fireball
▪ Caused by a larger object
o Falls and finds
▪ Ceplecha et al.
• Ablation = outside heating up to become bright
o Melting outside the rock
• Happens over a duration of a few seconds (the entire process)
• After fireball, dark rocks dropping to the ground (takes a while in
minutes [18km] to fall)
• Meteorites and Impact Crater
o Will it make a crater?
▪ How strong the rock is?
▪ Pluge pit
• Where do meteorites come from?
o Asteroid Belt
▪ About ~50 000 known meteorites - most of them from the Belt
• Meteorite Types
o Chondrite
▪ Fast cooling (shapes of crystals of olivine, pyroxene)
• What do they tell us?
o Type 3: ordinary chondrites, lot less matrix, lots of chondrules (mostly round),
iron-nickel grains
o Type 4: some have undergone metamorphism (recrystallize smallest crystals,
between the chondrules)
o Type 3 6 = recrystallize the crystals and give them enough energy so the
smaller crystals become larger crystals
▪ Start to lose the dark look of the matrix
▪ Start to lose the definition of the chondrules
▪ Small crystals have become larger and so can see the light
o Heat based metamorphism on these asteroids
▪ Capture heat in the inside and the heat on the outside is rapidly lost
• Inside traps and causes recrystallization
• Then it breaks up so it can get Type 4 and 5 from the inside
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