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Astronomy 2201B > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

What are the 5 bulk properties of planets?

A

Radius, density, uncompressed density, central pressure, and central temperature (inferred)

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2
Q

What is the primary material of the terrestrial planets?

A

Metals

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3
Q

What is the primary material of Jupiter/ Saturn

A

Hydrogen/Helium

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4
Q

What is the primary material of Uranus/Neptune

A

Ices

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5
Q

What is hydrostatic equilibrium?

A

The weight of the material above is balanced by the upward pressure

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6
Q

What is the net force in a hydrostatic equilibrium?

A

Zero net force (equilibrium)

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7
Q

To solve for the bulk density of a planet, what variables do we need to relate in a single equation?

A

Pressure, density and temperature (an equation of state)

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8
Q

Of what property is the melting point a function?

A

It is a function of pressure

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9
Q

Why can objects have a liquid outer core and a solid inner core?

A

Because the melting point is a function of pressure

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10
Q

What does a Phase Diagram tell us?

A

It tells us is a material is an a solid, liquid or gas state

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11
Q

Can material exist is more than one state?

A

Yes, even pure material can

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12
Q

What is the temperature range for the atmosphere and core of giant planets?

A

50-150K in the atmosphere and 10,000 - 20,000K in the core

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13
Q

The hydrogen and helium composition is inferred from what property?

A

It is inferred from the bulk density

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14
Q

At pressures below what values is H2 dominant in Jupiter and Saturn?

A

At pressure below 1 Mbar

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15
Q

What chemical process occurs to H2 at P>1Mbar?

A

The liquid H2 begins to dissociate to atomic H

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16
Q

At temperatures even higher than 3 Mbar, what can occur to the atomic helium?

A

It can become degenerate or turn into a plasma

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17
Q

What is an adiabat?

A

A line on a thermodynamic chart relating the pressure and temperature of a substance undergoing adiabatic change

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18
Q

What are the 3 main layers of hydrogen’s interior (from furthest to closest to the center)?

A

Molecular H, liquid metallic H, and rocky core

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19
Q

What does the highly conductive liquid metallic H layer allow to form on Jupiter?

A

A very strong magnetic field

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20
Q

How did the rocky/ icey core of Jupiter originally form?

A

It originally accumulated through gravity

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21
Q

What characteristic of the interaction between hydrogen and helium changes the temperature and pressure of Jupiter and Saturn?

A

Is the the miscibility (the ability for H and He to dissolve with each other) which can change T and P

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22
Q

Why does the miscibility of H and He have more of an effect on large planets like Jupiter and Saturn?

A

Because H and He don’t mix as well in lower temperatures

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23
Q

Saturn has the same 3 interior layers as Jupiter. In what proportions are they in comparison to Jupiter?

A

The Molecular H layer is much larger, and the liquid metallic H layer is much smaller in Saturn than in Jupiter

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24
Q

The fact that He sinks in H leads to what phenomenon?

A

Differentiation

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25
Q

What constitutes to majority of the ice in the solar system?

A

Water (solid water has at least 10 different crystallized forms)

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26
Q

What is the temperature range for the interiors of icy satellites?

A

T: 50 - 100K

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27
Q

What state is the water in the cores of the giant planets?

A

A sate called supercritical (neither liquid nor gas)

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28
Q

What are Uranus and Neptune largely composed of?

A

Water Ice (called “ice giants”)

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29
Q

What are Uranus and Neptune naturally ionized to?

A

H2O and OH- (at approx. 1 in i million parts)

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30
Q

Conductivity of the material in Uranus and Neptune account for what characteristic?

A

Magnetic Fields

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31
Q

What properties does the mineral composition of the terrestrial planets depend on?

A

On the temperature, pressure and relative abundance of constitutes

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32
Q

How deep does the earths mantle begin?

A

Approx. 5-70 km below the surface of the crust

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33
Q

How thick is Earth’s mantle and what percent of the Earth’s volume does is comprise?

A

Approx 2900km thick and 80% of the Earth’s volume

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34
Q

What is the Earth’s mantle primarily composed of?

A

Olivine (Mg,Fe)SiO4, and Pyroxene (Mg,Fe)Sio3

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35
Q

At what point so more densely structured minerals begin to take over the Earth’s Mantle?

A

At approx 400 km below to Earth’s surface

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36
Q

At what depth does the olive break down to periclase and enstatite?

A

Occurs at approx 660km

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37
Q

What material is the Earth’s core primarily composed of and how do we know this?

A

Iron, and we have inferred this from the bulk density

38
Q

Haw many solid phases is iron known to have?

A

5 (ex. alpha-Fe - “normal”, beta-Fe - “nonnormal”

39
Q

To what percent is the Earth’s core not pure iron?

A

Approx 5-10% (less dense than pure iron)

40
Q

The lower density of Earth’s core than pure iron indicate a mix of what elements?

A

A mix of S, O or H with Fe

41
Q

What is the diameter of the Earth’s core and what percent is this of the Earth’s diameter?

A

The Earth’s core is approx 7100 km in diameter and is about half of the diameter of the Earth

42
Q

At what depth does the Earth’s core change from liquid to solid?

A

The outermost 2250 km is liquid

43
Q

What part of the Earth’s interior drives the magnetic field?

A

Is is the liquid portion of the Earth’s core

44
Q

What is the temperature of the material directly below the Earth’s crust and at what rate does the temperature increase toward the center?

A

The material directly below the Earth’s crust is approx 1000 degrees Celsius and the temperature increases by about 1 degree Celsius / km

45
Q

What is the temperature range of the outer core?

A

Approx 3700 - 4300 degrees Celsius

46
Q

What is the temperature of the inner core?

A

Approx 7000 degree Celsius (hotter than the surface of the Sun)

47
Q

What is the equipotential surface of the planets called?

A

Geoid

48
Q

What is the lowest density layer of the Earth?

A

Its actually the crust (which floats on top of the mantle)

49
Q

How to we know that oceanic crust is more dense than continental crust?

A

Because is sits lower on the mantle (more density means more displacement)

50
Q

The sea cliffs and ridges that have risen 300 m above sea level have done so because of what process?

A

They have risen because of isostatic rebound

51
Q

How thick is Earth’s oceanic and continental crust?

A

Oceanic - as thin as 5km, Continental - up to 70 km

52
Q

What is the lithosphere?

A

Is encompasses both the crust and the rigid upper layers of the mantle (approx 80km thick)

53
Q

What is the asthenosphere?

A

It is the liquid and highly viscous layer of the mantle on which the crust floats

54
Q

What are 3 internal heat sources of planets?

A

Gravitational (accretion or differentiation), Radioactive decay, and Tidal dissipation

55
Q

What are the 4 main types of heat losses in planets?

A

Conduction, Radiation, Convection, and Plate Tectonics

56
Q

What is accretion heating?

A

The potential and kinetic energy of accreted bodies is converted largely into heat upon impact

57
Q

How does the speed of acceation affect the heating?

A

If accretion is slow, the heat will be radiated into space faster (body wont heat up as quickly). If the heating is fast, the heat will be “buried” (and the body’s T will increase)

58
Q

What is differential heating?

A

The potential energy of a system will be reduced if the more dense components sink to the center

59
Q

Why does differentiation not heat all SS bodies?

A

Differentiation can only occur in large hot bodies

60
Q

To what properties does the cooling time of bodies relate?

A

The cooling time is the ratio of a bodies energy content to the rate at which it radiates this energy

61
Q

What are the scarps on Mercury and how did they form?

A

The scarps are line of depression thought to have formed as Mercury shrunk as it cooled

62
Q

Why is an excess internal energy absorbed by the outer planets but not the terrestrial planets? (With the exception of Uranus)

A

The solar incident radiation on the outer planets is much less. Therefore, there cloud tops are much cool and can absorb more energy (vs. emission)

63
Q

What percent of Earth’s excess heat is due to radio activity?

A

Approx 50%

64
Q

How does tidal dissipation heat objects?

A

The friction created by the body and it is stretched creates heat

65
Q

What role does tidal heating play in Europa?

A

It keeps the subsurface ocean from freezing

66
Q

What is ohmic heating?

A

Eddy currents created by moving though the mag field dissipate heat

67
Q

What are the 2 types of seismic waves?

A

Body waves (S and P) and Surface Waves (Rayleigh and Love)

68
Q

What type of waves are “longitudinal, Congressional, and refractive along a direction of motion” and can travel through liquid

A

P waves (Primary, Push or Pressure)

69
Q

What type of waves “are oscillations transverse to propagation” and cannot travel to the core

A

S waves (Secondary, Shake, or Shear)

70
Q

What is the Moho or Mohorovicic discontinuity?

A

A discontinuity between the crust and the mantle where we see a jump in the P wave velocity

71
Q

Where else (other than between the crust and the mantle) do we find seismic discontinuities?

A

There are a few located in the upper mantle

72
Q

What are 5 methods we can use to learn about planetary interiors?

A

Seismology, Average Density, Magnetic Fields, Excess Heat, Surface Features

73
Q

What is the thickness of the Moon’s crust?

A

<5km under maria, up to .100km under the highlands

74
Q

What is the thickness of the mantle and what state is it in?

A

Approx 1400 km, the S wave velocity decreases therefore may be partially molten?

75
Q

What is the radius of the Moon’s core and what material is it mainly comprised of?

A

Its radius is approx 220-450 km and it is solid (P wave velocity increase) iron based

76
Q

Where are the seismically active zones on the Moon?

A

Near the surface (meteors) and 700-1200km down (tidal)

77
Q

How thick is Mercury’s lithosphere and what elements is it mainly composed of?

A

Approx 200km thick and composed of S, Na, and K

78
Q

How thick is Mercury’s mantle and what kind of minerals is it mainly composed of?

A

It is approx 600km thick and composed of rocky silicate minerals

79
Q

What percent of Mercury’s radius does its core take up and why does Mercury have such a strong magnetic field?

A

The core takes up approx 85% of the planet’s radius and is liquid in its outer layers, resulting in a strong magnetic field

80
Q

What is the reason that Venus has no tectonic activity?

A

Venus has no lower viscosity asthenosphere to lubricate any tectonic processes (as on Earth)

81
Q

Why does Venus lack a magnetic field?

A

It seems as though it has no liquid core (or at least no convection currents)

82
Q

Why does Mars have a low surface temperature?

A

It has a thick lithosphere

83
Q

What is the elevation difference between the northern and southern hemispheres on Mars?

A

Approx 5 km difference

84
Q

What compound is rich in Mar’s mantle?

A

Silicate (enriched in FeO)

85
Q

Does Mars have a thick liquid core?

A

No (inferred from its very weak magnetic field)

86
Q

To what is most of Jupiter’s internal heat attributed to?

A

Its gravitational contraction and accretion in the past

87
Q

From what region is Saturn’s magnetic field generated?

A

From the liquid metallic H region

88
Q

What two processes equally contribute to Saturn’s internal heat?

A

Gravitational contraction/accretion and the release of gravitational energy due to the “rainout” onto the core

89
Q

On both Uranus and Neptune, what scale is H and He found?

A

Only a few earth masses of material

90
Q

What characteristic (found in all the other planets) do Uranus and Saturn possibly lack?

A

A rocky core

Astronomy 2201B (11 decks)

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