Presentation Transcript
Impact Craters: Impact Craters
What are craters?: What are craters? Craters are bowl-shaped ground depressions created by:
1) volcanic eruptions,
2) bomb explosions, or
3) falling debris from space (impactors).
Candidates for impactors are asteroids, comets, and meteoroids.
Impactors: Impactors Asteroids: rocky leftover planetesimals of the inner solar system consisting of rocky and metallic substances. Ida and its satellite, Dactyl
Impactors: Impactors Most asteroids originate from the asteroid belt located between Mars and Jupiter.
Impactors: Impactors Comets: icy leftover planetesimals of the outer solar system. They are “dirty space snowballs” consisting of ice, gases, dust, and a rocky core. Comet Hyakutake
Impactors: Impactors Short period comets come from the Kuiper Belt.
Long period comets come from the Oort Cloud.
Impactors: Impactors Meteoroid: small debris left from comets or asteroid collisions.
Meteor: a meteoroid moving through the Earth’s atmosphere (a.k.a. a “shooting” or “falling” star).
Meteorite: a meteoroid that has fallen to the Earth’s surface.
Barringer Crater: Barringer Crater Approximately 1.2 km (0.75 mi.) wide and 200 m (650 ft.) deep.
Created about 50,000 years ago by a 50 m (150 ft.) meteorite.
Barringer Crater: Barringer Crater The impact gerated a blast of 20,000,000 tons of TNT upon impact.
Chicxulub Crater: Chicxulub Crater Located off the coast of Mexico’s Yucatan Peninsula.
At least 180 km (108 mi.) across and 45 km (27 mi.) deep.
Chicxulub Crater: Chicxulub Crater Created 65 million years ago by a
10-km (6 mi.)
impactor.
Extra-terrestial Craters: Extra-terrestial Craters Our moon was probably created when a Mars-size object collide with the forming Earth billions of years ago.
Callisto, a moon of Jupiter, is the most cratered body in our solar system.
Impact frequency: Impact frequency
Collisions: good or bad?: Collisions: good or bad? Good: early rain of rock and ice brought materials for the atmospheres, oceans, and polar caps to form. Could have also brought progenitors of life (amino acid compounds).
Bad: any impact with a fairly large impactor today would be catastrophic. Thus…