M&P Exam 02 Flashcards
What are the 3 main theories of moon formation? What bodies are associated with each?
Collision: Mars moons & Earth’s moon
Accretion: Jupiter’s moons
Capture: thought mars moons
How does accretion theory explain the formation of larger Jovian moons?
Dust & ice clumps spiral toward the young planet to form a disk around it with spiral density waves & satellitesimals that collect more material until they are stable moons.
Io & Europa formed in 6,000 years, callisto in 9 million years
Why do eccentric orbits slow down in accretion?
Orbits faster at perihelion & slower at aphelion
What problems were there in the belief that Mars’ moons were captured from solar orbits? Why is it unlikely?
Circular orbits & lack of second force to reduce their kinetic energy
Martian atmosphere could not have been tall enough to slow them down
Probability of other gravities being just right is very low
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What do simulations suggest about the formation of Mars’ moons?
Collisional formation
How was Earth’s moon formed?
Originally thought to be formed by accretion, but moon rocks indicate oxygen isotope abundances identical to earth rocks.
Lunar chemistry identical to earth’s chemistry
Impact Theory
Because of tides, moon’s orbital radius increases 38mm/yr
What causes the moon’s rotation period to match its orbital period?
Perturbation force that tugs harder on near side caused rotation period to equal the orbital period (synchronous rotation) & mascons on near side
What did the Grail Spacecraft look for? How?
Map local gravity strength using the distance between 2 probes, Ebb & Flow
Both satellites in same orbit, when 1 enters stronger gravity, it speed up
Laser measures distance between them & from gravity map, local lower density crust thickness can be calculates & then actual sizes of sub-mare craters
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How do the near and far side of the moon compare? Why is the far side cratered?
Lunar Prospector mission
Near side crust is 50km thinner
Radioactive Uranium & Thorium heated near side surface more (nucleosynthesis of thorium)
Higher surface gravity on near side under high density maria
What is significant about the Maria?
Large early impacts caused circular fractures in moon’s crust
Increased thermonuclear crust heating on the near side > lava flowed through cracks > cooled to form maria
What is the moon’s escape velocity?
2.4km/s = minimum impact velocity
What is the Sister Splash Theory?
Lunar collision with an early sister moon in orbit that got disturbed & collided at minimum impact velocity.
More low density crustal material deposited on far side
Thinner crust on near side caused mascons that led to synchronous rotation
How did the sister moon form?
At L4 or L5 of brother moon
Earth’s tides destabilize orbit & sister drifted away from its L point & they collide at minimum impact velocity
Sister formed at L5, decrease period… if formed at L4, increase period
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What solutions are there to the Sister Splash Theory?
Chemical analysis of Apollo lunar rocks on near side
Issues with communication on far side
Facts about IO
Larger than our moon
Orbital period = 42 hours
Phase-locked rotation
SO2 ice surface
Orbit synchronized to 2 other moons
Why are there active volcanoes on io?
Friction is generated when close to other moons & gravitational warping, causing orbital tidal distortions that cause magma heating.
This produces lava lakes and plumes of SO2.
Facts about Europa
Smaller than our moon
3.52 day orbital period
Phase-locked rotation
Water-ice Surface
Tidal Flexing => Heating caused by resonances with io & ganymede
Why do we think there is more water on Europa than on Earth?
Galileo Probe found evidence of subsurface ocean
Magnetic field fluctuates, suggesting mantle is electrically conducting & shifting due to briny water
Ice surface is shape-shifting => liquid beneath
Flew through a water plumes
What are Chaos Zones on Europa?
Dark, circular shapes caused by warm subsurface lakes & glacial flow to the surface
Liquid water cools & freezes, expanding causing the surface to crack. Water rises and collapses as ice
Possibly points of concentrated tidal heating
Lenticulae
What are Plumes on Europa?
Produced by fissures/cracks caused by pressure & shoot out ice
Location correlates with hot spots & contain H2O
What do ice fractures & impact cratering show on Europa?
Spectral line analysis shows they contain magnesium sulfate (Epsom Salt)
Few craters means surface is young (4-6 mil years old)
Describe Europa’s interior
20 km ice
80 km briny ocean
Rocky body & iron core
Describe the life sustaining “Black Smokers” on Europa
Hydrothermal vents on Earth spew heat & chemical nutrients caused by heat reservoirs below the ocean floor – perhaps necessary for life
What does the Europa Clipper Mission aim to observe?
Arrive in 2030 to investigate the interior of Europa from orbit by radar
Analyze ocean & ice shell, geology, composition
REASON: ice penetrating radar to tell us about water under ice
What will JUICE (Jupiter Ice Moons Explorer) Explore?
Characterize ocean layers & subsurface water, mass distribution, Ganymede atmosphere & magnetic field, interactions with Jovian magnetosphere
Facts about Ganymede
Largest moon in solar system
Ice covered surface
Dark areas older, lighter regions younger with organics due to impactors
What did Hubble Image on Ganymede?
Auroral belts & magnetic field that move over time => subsurface ocean
Perhaps suggest water vapor in the atmosphere
Facts about Callisto
Larger than our moon
Ice surface
Orbit not synchronized or tidally heated
Why can’t Mars support liquid water today?
Not enough atmospheric pressure to maintain liquid state
Describe the water phase diagram
Pressure & temperature axes
Triple point: point at a certain temperature and pressure where a substance can be in any 3 phases
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Why do ice skates glide?
Old Theory: blade pressure lowers freezing point => liquid layer, but freezing temperature is too high (31.9 F)
New Theory: Ice has a semi liquid outer layer & every 3rd molecule vibrates vertically. In ordinary ice, all water molecules are bound solid
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Draw Mars on the Phase Diagram
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Describe why there is no liquid CO2 on Mars
Liquid CO2 needs 5.1 atm at any T, neither Earth nor Mars has enough pressure
CO2 sublimates on Mars (solid to vapor) at a lower temperature than water, so permanent parts of polar ice caps and frost are water ice
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What evidence is there for ANCIENT liquid rocks on Mars?
Orbital photos of dry rivers & lakes (wake islands from water flow)
Hematite Crystals (blueberry rocks)
- Iron oxide in mineral form that crystallizes in aqueous solutions over 1,000 years
Layered terrain may be sedimentary (water flows & dumps mud)
Meteorites from Mars show signs of liquid erosion
- High energy impact ejects it from Mars & orbit around sun & collide with Earth
- Infused with water
What evidence is there for liquid water on Mars TODAY?
Martian Gullies of sandy soil
- No impact craters or wind blown erosion = young
- Dark rivulets = signs of water
- Aquifer source ~100 m down… sand puts enough pressure to have water in liquid state in a semi-permeable layer. Water evaporates at surface but it replenished
- Changes seen in gullies (falling sand)
How could Mars have had liquid oceans?
Need regions of pressure > 0.006 with temp > 0.01 C
Atmosphere must have had higher pressure
How do we know Mars had a thicker atmosphere?
NASA & U Colorado MAVEN (Mars Atmosphere & Volatile Evolution Probe)
- Determine how Mars lost its atmosphere & sample it
- Probe had 33 burn to slow it down & got captured into elliptical orbit, passes through upper atmosphere to sample every 4.5 hrs until it lost speed
What does it mean when a gas is “bottom up”?
Gas is absorbed into ground
Heavier isotopes sink in atmosphere so they escape less
What does it mean when a gas is “top down”?
Gas escapes from exosphere
2013 Curiosity indicated heavier isotopes are abundant on Mars
What are some “top down” models? How do gas molecules escape?
Model 1: Neutral Processes
- H gas in Martian atmosphere escapes
- H2 comes from dissociation of water in atmosphere, so water is depleted
- MAVEN: H escapes, O does not
Model 2: Solar Wind Stripping
- Solar UV ionizes upper atmosphere atoms & solar wind carries atoms away
- Mars has little atmosphere, so its ionosphere deflects ions, slowing solar wind stripping
- MAVEN: measured solar wind particles deep in Mars’ atmosphere… atoms may be combining above the ionosphere into neutral particles, then reionizing to carry away ions.
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What is the Martian Plume?
Plume of hot mantle material rising to lift the surface & causing volcanoes, so Mars is more active than we thought.
Methane, CO2, O2, H2O.
