Lecture 22 Flashcards
Asteroid
Stony or metallic mass that orbits the sun, often within the asteroids belt, with composition of planets, some with own moon, 10^1 to 10^6m
Comet
Dirty snowball (rock, dust, CO2, H2O) with tail of dust and gas, and with aphelion outside our solar system, 10^1 to 10^5 m
Meteroid
Stony, metallic, or carbonaceous with sun orbit, usually <10m diameter
Meteor
The particle or the light due to meteoroid interaction with atmosphere
Bolide
A large meteor that explodes in the atmosphere causing an airblast; ‘fireball’
Meteorite
Stony (chondrite) or metallic object that landed on Earth
Impact structure
Crater, or other evidence of extraterrestrial impact, ‘astrobleme’
NEO
Near earth object
PHO
Potentially hazardous object
Principle sources of comets
Kuiper-bent
Oort cloud
Why does earth have the poorest record of impact craters?
Atmosphere causes erosion
Why are impacts round?
Due to shear speed object is traveling
Disintegrates
Clearwater Canada
2 craters
Probably made by a double asteroid
Dating meteor craters
Dating with cosmogenic isotopes
10Be: 49,500 years
36Cl: 49,800 years
Chicxulub impact
Yucatan Peninsula
64 million years old
End of dinosaurs
106 miles in diameter
Chebarkul Event, 2013
Chelyabinsk Airblast
17m asteroid, 10,000 tons
17km/s
Blast altitude: 15-20 km
Equivalent energy of explosion: 500kT TNT
Tuguska Event, Siberia
Aerial explosion of stony asteroid, 25-30m diameter
10mT of TNT, 10 H-bombs
Sound heard over 1 mil km2
Flattened and burned 2000km2
Haughton crater
23km wide
1.8km deep
Significant fossil record
Early Miocene assemblage
Missing link skeleton
Collected from Haughton crater
Associated hazards of large impacts
Earthquake M11 Tsunami 1-3km in height Wildfires Nitrous oxides Dust creates winter Water vapour and CO2 create greenhouse summer Extinction
Cosmic radiation
Cancer, damage to tissue, damage to electronics
Depends on elevation
Depends on geomagnetic field
