Extraterrestrial Threats

Question 1

_____ objects have orbits that bring them close to Earth. _____ objects have orbits that cross Earth’s orbit. _____ objects are all objects that approach Earth.

Answer 1

Amor; Apollo; Near Earth.

Question 2

Small, icy body with eccentric elliptical orbits.

Answer 2

Comet.

Question 3

How fast do asteroids and comets travel?

Answer 3

Asteroids: 15-25km/sec.

Comets: 60-70km/sec.

Question 4

What is a meteoroid/meteor?

Answer 4

Significantly smaller than asteroids; small grains to <1m.

Question 5

What is a meteorite?

Answer 5

Solid piece of debris from asteroid, meteor, comet that survives passing through the atmosphere, reaching Earth’s surface.

Question 6

_____ is a meteorite large enough to create an impact crat

Answer 6

Bolide.

Question 7

Describe iron meteorites in terms of their frequency, composition, and where they are formed.

Answer 7

6% of all meteorites.

Iron and nickel.

Formed in core of planetary body.

Question 8

Describe stony-iron meteorites in terms of their frequency and composition.

Answer 8

<1% of all meteorites.

Magnesium and iron silicates.

Question 9

Describe chondrite meteorites in terms of their frequency and composition.

Answer 9

93% of all meteorites.

Stony, composition of mantle.

Question 10

This meteorite is similar to Earth’s rocks and made of basalt.

Answer 10

Achondrite.

Question 11

Round grains that form as molten droplets in space before being accreted.

Answer 11

Chondrules.

Question 12

What is meteorite flux?

Answer 12

The total mass of extraterrestrial objects that strike the Earth.

Question 13

How often do micrometeorites impact Earth?

Answer 13

Every 30 seconds.

Question 14

Regarding energy, what happens when a meteroite impacts Earth?

Answer 14

Kinetic energy converted to heat, vaporizing both asteroid and Earth material.

Question 15

Has a crater impact ever been observed by humans?

Answer 15

No.

Question 16

The jet of fragmented rock and dust from impact is _____.

Answer 16

Ejecta.

Question 17

Describe the shockwave of meteor impact.

Answer 17

Compression wave, then expansion wave (rarefaction, moves back to surface), floor of crater uplifted.

Question 18

_____ may occur around the crater.

Answer 18

Faulting.

Question 19

When ejecta settles back to Earth, it forms what? Where is this thickest and thinnest?

Answer 19

Ejecta blanket.

Thickest near crater, thins away from crater.

Question 20

Rocks in craters are not melted, but will be what?

Answer 20

Intensely fractured.

Question 21

List six pieces of evidence of impacts.

Answer 21

Shatter cones.

Intense shock.

Shocked quartz.

Spherules: melted ejecta falls back to Earth.

Crater and gravity surveys.

Iridium in abnormally high concentration.

Question 22

Would a meteor impact cause earthquakes?

Answer 22

Massive earthquakes (>10 Richter), may trigger multiple worldwide and volcanic eruptions.

Question 23

Meteors may cause megatsunamis. What is this dependent on? A 10km diameter object could produce how high a wave?

Answer 23

Depth of water and if impact is in ocean.

1-3km high wave.

Question 24

Material blasted into atmosphere from impact re-enter atmosphere. What are consequences of this?

Answer 24

Heats up atmosphere, possibly igniting wildfires.

Question 25

What are the potential climate impacts of a meteor impact?

Answer 25

Dust, other ejecta, and sulphate could block sunlight, causing cooling.

Sudden pulse of carbon dioxide by vaporization of carbonate could lead to global warming.

Question 26

How would dust and other ejecta blocking sunlight affect life?

Answer 26

Photosynthesizing plants die, disrupting food chain.

Question 27

_____ aerosols and _____ combines with precipitation producing acid rain and acidification of surface water

Answer 27

Sulfate; nitrous oxide.

Question 28

The Chicxulub asteroid ejected enough material to do what?

Answer 28

Cover Earth in layer of dust.

Question 29

What was the Tunguska Event? How much forest did it flatten, and what was its estimated energy?

Answer 29

Airburst of an asteroid or comet 5-10km above surface.

Flattened 2000km2 forest.

Energy estimated 10-30Mt of TNT.

Question 30

List the recurrence interval for:

• 1 micron diameter
• 1 mm diameter
• 1 m diameter
• 100 m diameter
• 10 km diamater

Answer 30

1 micron: 30 microseconds

1 mm: 30 seconds.

1 m: 1 year.

100 m: 10,000 years.

10 km: 100,000,000 years.