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Astronomy 2201B > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

The following describes which SS body: Highly cratered surfaces, large ring basins, cracks and scarps, surface is relatively low relief with no major continents for mountain structures

A

Mercury

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2
Q

The following describes which SS body: little surface relief and very few craters of any size

A

Venus

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3
Q

The following describes which SS body: Bright and heavily cratered highlands, and dark smooth maria. Maria cover approx 20% of the surface

A

The Moon

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4
Q

The following describes which SS body: craters, volcanoes, plains, and canyons. Clear signs of evolution caused by a variety of factors including internal heating, tectonics, impacts, wind, and water

A

Mars

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5
Q

The study of rocks, their structure, composition and origin is called

A

Petrology

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6
Q

What is the compositional relationship between rocks and minerals?

A

Rocks are made of one or more minerals

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7
Q

A solid chemical compound that occurs naturally (can be different if they are made of the same components but different structure

A

Minerals

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8
Q

What type of mineral composes the majority of the Earth’s crust and mantle?

A

Silicate (silicon and oxygen)

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9
Q

What are the 3 main families of silicate?

A

Olivine (most dense), Pyroxene (chains), and Feldspar (least dense)

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10
Q

What family of silicates make up approx 60% of Earth’s rock?

A

Feldspar

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11
Q

What are the two categories of feldspar and how are they differentiated?

A

Othoclase (potassium rich), and Plagioclase (sodium rich)

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12
Q

Which mineral is most common on the icy planets?

A

Water and methane

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13
Q

How are rocks classified?

A

By their mineral content and their formation history

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14
Q

What are primitive rocks?

A

Rocks formed in the protosolar nebula, with element ratios the same as solar abundances (only examples are chondritic meteorites)

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15
Q

How is igneous rock formed?

A

Through the crystallization of rock melted in the crust or upper mantle

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16
Q

What are the 2 categories of igneous rock?

A

Intrusive and extrusive

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17
Q

How does sedimentary rock form?

A

Through the deposition, burial, and lithification of rock that has been weathered through exposure at the surface of the crust

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18
Q

What type of rock is biological (fossils of animal shells)

A

Limestone

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19
Q

How is metamorphic rock formed?

A

Through the recrystalization of minerals under high temperature and pressure in the deep and upper mantle (can also be formed by impact)

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20
Q

Give one example of each of the 3 main types of rock

A

Igneous - Granites, Metamorphic - marble, Sedimentary - sandstone

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21
Q

Who discovered the first lunar craters?

A

Galelio

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22
Q

When were the first craters discovered on Earth?

A

It wasnt until the 20th century

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23
Q

What are impact craters circular?

A

Because the material is blasted out equally in all directions (although the depth may be asymmetrical due to the impact angle)

24
Q

How many times larger are the impact craters relative to the impactor?

A

Approx 10x larger

25
Q

When are shock waves created by impactors?

A

When the impact velocity is greater than the speed of sound

26
Q

A highly compressed zone with a high density of energy and matter is what?

A

A shock

27
Q

What happens to the rock as a shock wave carries the energy of the explosion into the ground?

A

The rock will compress and deform like a fluid

28
Q

The rebound of the inner material of a crater forms what?

A

A central peak

29
Q

What for the rim (and maybe rays) around an impact crater?

A

The fragments that were ejected from the surface

30
Q

What are the 3 steps to finding the impact energy?

A
  1. Find the mass., 2. Find the kinetic energy., 3. Convert to megatons
31
Q

What what velocity must an object be moving to become an explosion upon impact?

A

3km/s or faster

32
Q

What is the max diameter of a microcrater?

A

10 microns

33
Q

What property of lunar material can be explained by microcraters?

A

The age of the lunar material

34
Q

The fine powder created by impacts that covers the surface of the Moon is called what?

A

Regolith

35
Q

How thick is the lunar regolith on the highlands and the maria?

A

Approx 2km thick in the uplands and approx 10 m thick over the maria

36
Q

What method of dating craters do we use on inactive worlds?

A

We can compare the radioactive dating age to the number density of craters on the surface

37
Q

Why cant we use the number density of craters on the surface of active worlds to ascertain an age?

A

Wind and water erosion can destroy craters (lowering the number density)

38
Q

What can we tell about small craters found on the surface of active worlds?

A

These craters have to be young (and therefore unaffected by weathering)

39
Q

How can we ascertain the age of other SS bodies if we know their crater number density but cannot gather material for radioactive dating?

A

We can compare their number density to that of the Moon and extrapolate their age (only for inactive worlds)

40
Q

What is the cratering saturation equilibrium?

A

When the cratering density gets too high new craters begin to obliterate the old ones and the density reaches a constant

41
Q

What is the minimum age range for SS objects that have reached cratering saturation equilibrium?

A

3.9-4.5 years old

42
Q

What factor can affect the cratering rate of object?

A

Proximity to large bodies (more massive bodies attract more asteroids/planetesimals)

43
Q

How do we know that the Marian moon Phobos is very old?

A

Its surface is heavily cratered

44
Q

How do we know that the Marian moon Deimos is younger than its companion moon, Phobos?

A

Although it is still very close to saturation, it’s surface is less cratered than Phobos

45
Q

What is the relationship in Jupiter’s moons between distance from Jupiter and bulk density?

A

The further the moon is from Jupiter, the lower its bulk density

46
Q

How old are the surfaces of the Galilean moons relative to each other?

A

Callisto has the oldest surface, Ganymede has some younger areas and some older areas, Europa has a younger surface (fractured and icy) and Lo has a very young face (no impact craters)

47
Q

What type of heating drives all geological heating on Jupiter’s moons?

A

Tidal Heating

48
Q

What feature distinguishes Iapetus (Saturn’s moon)?

A

One side is jet black (possibly dust from another moon, Phoboe) and the other side is bright (water ice)

49
Q

What feature distinguishes Encleadus (Saturn’s moon)?

A

It has plumes (possibly of water) as the result of continuous heating and due to long lived isotopes and tidal forces

50
Q

What is thought to be the origin of Triton (Moon of Neptune) and Pluto?

A

Thought to both have originally been members of the Kuiper Belt

51
Q

What is the approximate surface area of Mercury?

A

> 3Ga

52
Q

Why cant small meteorites reach the surface of Venus?

A

These small meteorites cannot penetrate the atmosphere

53
Q

Why is the surface of Venus so young?

A

There is little erosion but there is much erasure from volcanoes

54
Q

Why is the Earth’s crater density lower than that of the Moon?

A

Because small craters are eroded

55
Q

Which Marian hemisphere is “old and which is “young”?

A

The south is the “old” half and the north is the “young” half

56
Q

What evidence for the past presence of water do we have on Mars?

A

We can see splash craters, signs of water erosion, and craters that seemed to have formed in mud

Astronomy 2201B (11 decks)

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