Extraterrestrial Threats Flashcards
(30 cards)
_____ objects have orbits that bring them close to Earth. _____ objects have orbits that cross Earth’s orbit. _____ objects are all objects that approach Earth.
Amor; Apollo; Near Earth.
Small, icy body with eccentric elliptical orbits.
Comet.
How fast do asteroids and comets travel?
Asteroids: 15-25km/sec.
Comets: 60-70km/sec.
What is a meteoroid/meteor?
Significantly smaller than asteroids; small grains to <1m.
What is a meteorite?
Solid piece of debris from asteroid, meteor, comet that survives passing through the atmosphere, reaching Earth’s surface.
_____ is a meteorite large enough to create an impact crat
Bolide.
Describe iron meteorites in terms of their frequency, composition, and where they are formed.
6% of all meteorites.
Iron and nickel.
Formed in core of planetary body.
Describe stony-iron meteorites in terms of their frequency and composition.
<1% of all meteorites.
Magnesium and iron silicates.
Describe chondrite meteorites in terms of their frequency and composition.
93% of all meteorites.
Stony, composition of mantle.
This meteorite is similar to Earth’s rocks and made of basalt.
Achondrite.
Round grains that form as molten droplets in space before being accreted.
Chondrules.
What is meteorite flux?
The total mass of extraterrestrial objects that strike the Earth.
How often do micrometeorites impact Earth?
Every 30 seconds.
Regarding energy, what happens when a meteroite impacts Earth?
Kinetic energy converted to heat, vaporizing both asteroid and Earth material.
Has a crater impact ever been observed by humans?
No.
The jet of fragmented rock and dust from impact is _____.
Ejecta.
Describe the shockwave of meteor impact.
Compression wave, then expansion wave (rarefaction, moves back to surface), floor of crater uplifted.
_____ may occur around the crater.
Faulting.
When ejecta settles back to Earth, it forms what? Where is this thickest and thinnest?
Ejecta blanket.
Thickest near crater, thins away from crater.
Rocks in craters are not melted, but will be what?
Intensely fractured.
List six pieces of evidence of impacts.
Shatter cones.
Intense shock.
Shocked quartz.
Spherules: melted ejecta falls back to Earth.
Crater and gravity surveys.
Iridium in abnormally high concentration.
Would a meteor impact cause earthquakes?
Massive earthquakes (>10 Richter), may trigger multiple worldwide and volcanic eruptions.
Meteors may cause megatsunamis. What is this dependent on? A 10km diameter object could produce how high a wave?
Depth of water and if impact is in ocean.
1-3km high wave.
Material blasted into atmosphere from impact re-enter atmosphere. What are consequences of this?
Heats up atmosphere, possibly igniting wildfires.
