Chapter 8 Flashcards
What are the 5 bulk properties of planets?
Radius, density, uncompressed density, central pressure, and central temperature (inferred)
What is the primary material of the terrestrial planets?
Metals
What is the primary material of Jupiter/ Saturn
Hydrogen/Helium
What is the primary material of Uranus/Neptune
Ices
What is hydrostatic equilibrium?
The weight of the material above is balanced by the upward pressure
What is the net force in a hydrostatic equilibrium?
Zero net force (equilibrium)
To solve for the bulk density of a planet, what variables do we need to relate in a single equation?
Pressure, density and temperature (an equation of state)
Of what property is the melting point a function?
It is a function of pressure
Why can objects have a liquid outer core and a solid inner core?
Because the melting point is a function of pressure
What does a Phase Diagram tell us?
It tells us is a material is an a solid, liquid or gas state
Can material exist is more than one state?
Yes, even pure material can
What is the temperature range for the atmosphere and core of giant planets?
50-150K in the atmosphere and 10,000 - 20,000K in the core
The hydrogen and helium composition is inferred from what property?
It is inferred from the bulk density
At pressures below what values is H2 dominant in Jupiter and Saturn?
At pressure below 1 Mbar
What chemical process occurs to H2 at P>1Mbar?
The liquid H2 begins to dissociate to atomic H
At temperatures even higher than 3 Mbar, what can occur to the atomic helium?
It can become degenerate or turn into a plasma
What is an adiabat?
A line on a thermodynamic chart relating the pressure and temperature of a substance undergoing adiabatic change
What are the 3 main layers of hydrogen’s interior (from furthest to closest to the center)?
Molecular H, liquid metallic H, and rocky core
What does the highly conductive liquid metallic H layer allow to form on Jupiter?
A very strong magnetic field
How did the rocky/ icey core of Jupiter originally form?
It originally accumulated through gravity
What characteristic of the interaction between hydrogen and helium changes the temperature and pressure of Jupiter and Saturn?
Is the the miscibility (the ability for H and He to dissolve with each other) which can change T and P
Why does the miscibility of H and He have more of an effect on large planets like Jupiter and Saturn?
Because H and He don’t mix as well in lower temperatures
Saturn has the same 3 interior layers as Jupiter. In what proportions are they in comparison to Jupiter?
The Molecular H layer is much larger, and the liquid metallic H layer is much smaller in Saturn than in Jupiter
The fact that He sinks in H leads to what phenomenon?
Differentiation
What constitutes to majority of the ice in the solar system?
Water (solid water has at least 10 different crystallized forms)
What is the temperature range for the interiors of icy satellites?
T: 50 - 100K
What state is the water in the cores of the giant planets?
A sate called supercritical (neither liquid nor gas)
What are Uranus and Neptune largely composed of?
Water Ice (called “ice giants”)
What are Uranus and Neptune naturally ionized to?
H2O and OH- (at approx. 1 in i million parts)
Conductivity of the material in Uranus and Neptune account for what characteristic?
Magnetic Fields
What properties does the mineral composition of the terrestrial planets depend on?
On the temperature, pressure and relative abundance of constitutes
How deep does the earths mantle begin?
Approx. 5-70 km below the surface of the crust
How thick is Earth’s mantle and what percent of the Earth’s volume does is comprise?
Approx 2900km thick and 80% of the Earth’s volume
What is the Earth’s mantle primarily composed of?
Olivine (Mg,Fe)SiO4, and Pyroxene (Mg,Fe)Sio3
At what point so more densely structured minerals begin to take over the Earth’s Mantle?
At approx 400 km below to Earth’s surface
At what depth does the olive break down to periclase and enstatite?
Occurs at approx 660km
What material is the Earth’s core primarily composed of and how do we know this?
Iron, and we have inferred this from the bulk density
Haw many solid phases is iron known to have?
5 (ex. alpha-Fe - “normal”, beta-Fe - “nonnormal”
To what percent is the Earth’s core not pure iron?
Approx 5-10% (less dense than pure iron)
The lower density of Earth’s core than pure iron indicate a mix of what elements?
A mix of S, O or H with Fe
What is the diameter of the Earth’s core and what percent is this of the Earth’s diameter?
The Earth’s core is approx 7100 km in diameter and is about half of the diameter of the Earth
At what depth does the Earth’s core change from liquid to solid?
The outermost 2250 km is liquid
What part of the Earth’s interior drives the magnetic field?
Is is the liquid portion of the Earth’s core
What is the temperature of the material directly below the Earth’s crust and at what rate does the temperature increase toward the center?
The material directly below the Earth’s crust is approx 1000 degrees Celsius and the temperature increases by about 1 degree Celsius / km
What is the temperature range of the outer core?
Approx 3700 - 4300 degrees Celsius
What is the temperature of the inner core?
Approx 7000 degree Celsius (hotter than the surface of the Sun)
What is the equipotential surface of the planets called?
Geoid
What is the lowest density layer of the Earth?
Its actually the crust (which floats on top of the mantle)
How to we know that oceanic crust is more dense than continental crust?
Because is sits lower on the mantle (more density means more displacement)
The sea cliffs and ridges that have risen 300 m above sea level have done so because of what process?
They have risen because of isostatic rebound
How thick is Earth’s oceanic and continental crust?
Oceanic - as thin as 5km, Continental - up to 70 km
What is the lithosphere?
Is encompasses both the crust and the rigid upper layers of the mantle (approx 80km thick)
What is the asthenosphere?
It is the liquid and highly viscous layer of the mantle on which the crust floats
What are 3 internal heat sources of planets?
Gravitational (accretion or differentiation), Radioactive decay, and Tidal dissipation
What are the 4 main types of heat losses in planets?
Conduction, Radiation, Convection, and Plate Tectonics
What is accretion heating?
The potential and kinetic energy of accreted bodies is converted largely into heat upon impact
How does the speed of acceation affect the heating?
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)
What is differential heating?
The potential energy of a system will be reduced if the more dense components sink to the center
Why does differentiation not heat all SS bodies?
Differentiation can only occur in large hot bodies
To what properties does the cooling time of bodies relate?
The cooling time is the ratio of a bodies energy content to the rate at which it radiates this energy
What are the scarps on Mercury and how did they form?
The scarps are line of depression thought to have formed as Mercury shrunk as it cooled
Why is an excess internal energy absorbed by the outer planets but not the terrestrial planets? (With the exception of Uranus)
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)
What percent of Earth’s excess heat is due to radio activity?
Approx 50%
How does tidal dissipation heat objects?
The friction created by the body and it is stretched creates heat
What role does tidal heating play in Europa?
It keeps the subsurface ocean from freezing
What is ohmic heating?
Eddy currents created by moving though the mag field dissipate heat
What are the 2 types of seismic waves?
Body waves (S and P) and Surface Waves (Rayleigh and Love)
What type of waves are “longitudinal, Congressional, and refractive along a direction of motion” and can travel through liquid
P waves (Primary, Push or Pressure)
What type of waves “are oscillations transverse to propagation” and cannot travel to the core
S waves (Secondary, Shake, or Shear)
What is the Moho or Mohorovicic discontinuity?
A discontinuity between the crust and the mantle where we see a jump in the P wave velocity
Where else (other than between the crust and the mantle) do we find seismic discontinuities?
There are a few located in the upper mantle
What are 5 methods we can use to learn about planetary interiors?
Seismology, Average Density, Magnetic Fields, Excess Heat, Surface Features
What is the thickness of the Moon’s crust?
<5km under maria, up to .100km under the highlands
What is the thickness of the mantle and what state is it in?
Approx 1400 km, the S wave velocity decreases therefore may be partially molten?
What is the radius of the Moon’s core and what material is it mainly comprised of?
Its radius is approx 220-450 km and it is solid (P wave velocity increase) iron based
Where are the seismically active zones on the Moon?
Near the surface (meteors) and 700-1200km down (tidal)
How thick is Mercury’s lithosphere and what elements is it mainly composed of?
Approx 200km thick and composed of S, Na, and K
How thick is Mercury’s mantle and what kind of minerals is it mainly composed of?
It is approx 600km thick and composed of rocky silicate minerals
What percent of Mercury’s radius does its core take up and why does Mercury have such a strong magnetic field?
The core takes up approx 85% of the planet’s radius and is liquid in its outer layers, resulting in a strong magnetic field
What is the reason that Venus has no tectonic activity?
Venus has no lower viscosity asthenosphere to lubricate any tectonic processes (as on Earth)
Why does Venus lack a magnetic field?
It seems as though it has no liquid core (or at least no convection currents)
Why does Mars have a low surface temperature?
It has a thick lithosphere
What is the elevation difference between the northern and southern hemispheres on Mars?
Approx 5 km difference
What compound is rich in Mar’s mantle?
Silicate (enriched in FeO)
Does Mars have a thick liquid core?
No (inferred from its very weak magnetic field)
To what is most of Jupiter’s internal heat attributed to?
Its gravitational contraction and accretion in the past
From what region is Saturn’s magnetic field generated?
From the liquid metallic H region
What two processes equally contribute to Saturn’s internal heat?
Gravitational contraction/accretion and the release of gravitational energy due to the “rainout” onto the core
On both Uranus and Neptune, what scale is H and He found?
Only a few earth masses of material
What characteristic (found in all the other planets) do Uranus and Saturn possibly lack?
A rocky core
