Chapter 6

Question 1

What is the name of a solid particle in orbit about the Sun: composed of silicates and hydrocarbons; typically lower density than common terrestrial rock?

Answer 1

Meteoroid

Question 2

A meteoroid which survives entry into atmosphere and lands on Earth’s surface

Answer 2

Meteoroite

Question 3

The light heat and sound phenomena produced when a meteoroid enters the Earth’s atmosphere and is heated through collision with air molecules

Answer 3

Meteor

Question 4

Groups of meteoroids which move in

similar orbits after being ejected from a comet

Answer 4

Meteor Stream

Question 5

When a meteor stream’s orbit intersects with Earth’s to produce meteors

Answer 5

Meteor Shower

Question 6

A short-lived, usually strong meteor shower usually occurring at the perihelion passage of the parent comet

Answer 6

Meteor Storm

Question 7

What are the 2 sources of meteorites?

Answer 7

Comets and asteroids

Question 8

Where do small meteoroids come from?

Answer 8

Comet nucleus release silicate and other solids as they pass near the sun (dust tails)

Question 9

When does gas vaporization stop turn into dust tail?

Answer 9

Around 1.5 to 2 AU

Question 10

How many major meteor shower are their in one year?

Answer 10

13 major showers

Question 11

Do small meteors ever reach the Earth’s surface?

Answer 11

No, they entirely turn to vapor in the Earth’s atmosphere, atoms are exited and radiate away as they relax

Question 12

What is a sporadic meteoroid?

Answer 12

A meteoroid that used to be part of a stream, but has diffused away from the stream after a long period of time

Question 13

What is the size at which a metor is too small to vaporize and survives to surface?

Answer 13

Less than 10 mu*m

Question 14

What size meteors have portions which survive to the surface?

Answer 14

a few cm to tens of m (depends on initial velocities, >30km/s will totally ablate)

Question 15

What is the primary source of meteorites?

Answer 15

Asteroid collisions (can send large particle into Earth’s orbit)

Question 16

How many “fireballs” have be perturbed out of the asteroid belt?

Answer 16

Approx 25 have been recorded

Question 17

What is ablation?

Answer 17

Vaporization due to firction with the atomsphere

Question 18

Why are meteorites cold when they impact?

Answer 18

They move so fast that only the outer mm to cm are melted, when the reach the upper atmosphere they are in “dark fall” and cool down

Question 19

What are the 4 major types of meteorites found?

Answer 19

Stony (chondrites/achondrites), Irons (Fe and Ni), Stony-Irons (mix of rock and metal), Lunar/Martian

Question 20

Which of these subcategories fall under undifferentiated?

Answer 20

Chondrites (the rest are differentiated)

Question 21

What is the difference between differentiated and undifferentiated meteorites?

Answer 21

Undifferentiated - unheated, differentiated - heated

Question 22

Where are “old” meteorites found?

Answer 22

Found in hot or cold deserts (harder to spot)

Question 23

How many “new” meteorites are found each year?

Answer 23

Approx 6, found all over the world

Question 24

What percent of the SS meteorites are Stony?

Answer 24

Approx 60%

Question 25

Which type of meteorite is the oldest?

Answer 25

Chondrites, grains (condrules) condensed out of the SS approx 4.5 billion years ago

Question 26

how large does a pp have to be fore rock to begin melting?

Answer 26

It muct be greater the 100 km across

Question 27

What is differentiation?

Answer 27

As rocks melt, heavier elements (ie. iron) sink to the center and lighter rock rises the the surface

Question 28

What percent of SS meteorites are Iron? Where do they come from?

Answer 28

Approx 5% , come from broken, cooled down cores of larger bodies

Question 29

What are regmeglypts

Answer 29

Thumb-print like depressions on iron meteroites, formed when melting in their Earth-decent

Question 30

What are Widmanstatten patterns

Answer 30

Patterns made in pure iron-nickel alloy that occurs only in very slow cooling

Question 31

What percent of SS meteorites are Stony-iron?

Answer 31

About 10%, can be very difficult to distinguish from just their surface

Question 32

What type of meteorites do Lunar meteorites fall under?

Answer 32

Achondrites, most common are anothositic breccias (rich in Al-Ca)

Question 33

How do we know which meteorites come from the moon?

Answer 33

Lunar meteorites all have composition similar to the samples taken from the Apollo Mission

Question 34

Which planet is the only one whose meteorits have been found?

Answer 34

Mars, although its strong gravity makes it them more rare than lunar

Question 35

Why is ALH84001.0 special?

Answer 35

It is the oldest/ largest Martian meteorite ever found, was thought to contain fossil bacteria (not believed anymore)

Question 36

What are the 3 distinct ages of meteorites?

Answer 36

Formation (time since it was liquid/gas), Gas retention (last shocked/ strongly heated), Cosmic Ray Exposure

Question 37

What was the largest meteoric impact in history?

Answer 37

The Tunguska Effect (June 30th, 1908)

Question 38

On what scale would the damage be if Earth was impacted by a meteor 100m to 1km in diameter?

Answer 38

Country to continental scale

Question 39

What diameter must an asteroid be to cause dust to be ejected into the atmosphere and cool the Earth?

Answer 39

Diameter >1km

Question 40

About how many >1km diameter meteors cross the Earth’s orbit? How often should the globe be concerned?

Answer 40

Approx 1000, once every million years

Question 41

How often should there be “local” concern for meteor impact?

Answer 41

Once every 1000 years, on average

Question 42

What is currently the best strategy for avoiding meteor impact?

Answer 42

Improve out ability to detect these objects (bigger telescopes and better cameras)