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ASTR 121 Midterm #2
Midterm 2/3
84
Astronomy
Undergraduate 1
11/01/2010

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Term
Why is the Earth Unique?
Definition
Vast amounts of liquid water, ability to sustain intelligent life.
Term
Average Density of Earth
Definition
5.5 gm/cc
Term
2 Types of Seismic Waves Studied from Earthquakes:
Definition
Pressure/ P waves: travel through liquid or solids.

Shear/ S waves: cannot propgate liquids or gases due to lack of lateral restoring foreces.
Term
How Fast to Seismic Waves Travel?
Definition
10km/sec
Term
4 Layers of Earth and their densities:
Definition
1)crust, 3.3gm/cc (metals/ silicates= basalt)
2)semi solid mantle 3.5-5.5 gm/cc (olivine Fe oxides)
3)liquid outer core 9-11 gm/cc (molten Fe)
$)solid inner core 17 gm/cc (Fe, Ni)
Term
Temp of Earth Core?
Definition
6200K, and lighter densities are on top.
Term
Percentage of earth to water on Earth?
Definition
29% earth, 71% water
Term
How do we know that the continents on earth are moving?
Definition
Fossil Records.
Term
Dry Land of Earth is composed of:
Definition
Igneous Rock: Formed from molten material, basalt granite.

Sedimentary Rok- minterals cemented by pressure, sandstone and limestone.

Metamorphic Rock- Igneous or sedimentary rock that is subjected to high temp and press. such as marble.
Term
What is Earths Crust Shaped by?
Definition
1) impact cratering
2)erosion
3)thermal tectonic activity
Term
How many crustal plates and how fast are they moving on earth?
Definition
12, few cm per 100 years.
Term
4 types of boundaries between plates:
Definition
1) mid-ocean ridge
2)sliding plates
3) ocean trench
4)mountains
Term
Young mountains vs. Old mountains
Definition
Sharp and irregular vs low and rounded.
Term
7 stages of earths Atmospheric Evolution:
Definition
1)proto-atmosphere phase: thick and rich in light elements
2)early atmosphere phase: orignal lost, due to heating, and gravity
3)secondary atomsphere phase: Atmosphere rich from outgassing ( H20, C02, N2, SO2)
4)cooling phase: H20 rained out of atmosphere
5) photodisintegration: extra water vapor converting into h2 and CO2
6) Carbonate Rock fromation: H2- and Co2 reat in the oceans to become carbonate rocks and O2
7)life: Turns co2 into O2.
Term
What is Earth Atmosphere today?
Definition
78% N2, 21%O2, 1% Ar, and trace amonts of H20, CO2, Ne, Xe.
Term
Why does the Earth have strong mag field?
Definition
Iron Core.
Term
Why is earths magnetic field distorted?
Definition
Solar Wind (prtons and electrons)
Term
Van Allen Belt:
Definition
Magnetic mirror that traps high energy particles headed for the earth and sends them to the poles, when they interact with the atmosphere you get aurora.
Term
Size and Distance of Moon and rotation period:
Definition
384,403km from earth, 3476 km in diameter, revoltuion around earth takes 27 days, 7 hours, 43 min.
Term
Ration of mass of Moon/Earth?
Definition
1/80
Term
Average Density of Moon?
Definition
3.37 g/cm^3 (similar to the crust of the earth, basaltic sillicates)
Term
Surface and Albedo of Moon, and gravity vs earths?
Definition
Grey/tan with albedo of .07, and 1/6th of the gravity.
Term
3 major features on the moon?
Definition
1)craters 2) highlands 3) Maria
Term
Erosion on world (moon) with no atmosphere caused by?
Definition
1) slumping (gravity)
2)other impacts
3)temp changes
4)moonquakes
Term
Soil age on Maria Vs. Highland
Definition
Newer, older. and respectively 4x10^9/4.6x109
Term
How long has the moon been geologically dead? how do you know?
Definition
3.5 bill years. No rocks younger have been found.
Term
4 periods in the geological history of the moon:
Definition
>cooled and solidified 4.4 bill years ago
>between 4.4-4.2 bill years, heavy bombardment (<10km in size)
>3.9 bill years, moon is tidally locked, and more bombardment (>100km in size) and created maria, and cracks and fissures.
Term
Possibilities for lunar origin: 3)
Definition
1) part of earth, not likely due to elements
2) formed near mars.
3)fissioned from earth mantle.
Term
Radii of Mercury:
Definition
2440 km
Term
Greatest elongation of mercury:
Definition
28 degrees
Term
Mean density of Mercury?
Definition
5.4 g/cc, implies dense iron core, probably solid, due to low mass, and cooling.
Term
Mercuries Resonance:
Definition
2/3, tidally locked with mars. Rotation=58.6 and Orbital period= 87.9 days.
Term
Range of Temp's on Mercury:
Definition
100k-700k! This is due to the lack of any significant atmosphere.
Term
Surface Features of Mercury:
Definition
Heavily cratered, very few maria (cooled faster than the moon), cratering is less heavy, more plain region between craters due to higher surface gravity on mercury (debris doesn't fly far)
Term
Equation for Surface Gravity:
Definition
g=GM/R^2
Term
Magnetic Field on Mercury?
Definition
Strong, Iron in core, stayed molten for a long time.
Term
Venus is a morning star and evening star: what were the two planets it was once thot to be?
Definition
Phosphorous, Hesperus
Term
Why is Venus Called the Twin Planet?
Definition
1) similar radius/ size 2)similar mass 3)similar density 4)has an atmosphere
Term
Temp of Venus, what is atmosphere made up of?
Definition
800 F, carbon dioxide, sulfuric acid.
Term
Vesnusian Atmosphere:
Definition
97% Co2, 2% N2, less than 1% everything else, Lots of sulfuric acid in lower atmosphere.
Term
P=NkqT
Definition
Pressure=Avagados constant times the botlzmann constant times the density times the temp.
Term
P2/P1=(q2/q1)(T2/T1)
Definition
relating the pressure density and temp of 2 planets.
Term
What is the 890 degrees F on Venus Caused By
Definition
Runaway Greenhouse effect with CO2
Term
What are some of the effects of an enhanced Greenhouse effect?
Definition
1)global warming, 3-5 C by 2050
2)increased cloud cover
3)increased hurricane strengths.
4)rise in seal level by 1 to 2 m over nxt 50 years
5)increased growing season at northern latitudes.
Term
Venusian Surface Features:
Definition
1)Craters 2) Volcanos 3)Fault Lines 4) Arachnoids (upwelling of magma from interior of planet creaing oval concentric rings.)
Evidence of Erosion!
Term
Notable Surface Features on Mars:
Definition
1) Valleys and Canyons (Valles Marineris canyon System)
2)Landslides
3)Islands (caused by tremendous water flow)
4)Outflows (caused by rapid running of water, when unfrozen)
5)Polar Caps (CO2 Ice)
Term
2 Moons of Mars:
Definition
Phobos and Deimos (Fear and Panic) they are captured astroids.
Term
Other Surface Features on Mars:
Definition
1)Craters with heavy erosion due to atmosphere
2) Featureless terrain (not Maria)
3)Chaotic terrain: highlands and broken hills, old tectonic regions.
4) Volcanos (Olympus Mons)
Term
Mass1/Mass2=Vol1/Vol2=(height1/height2)^3
Definition
use for volcanos.
Term
H20 on Mars
Definition
Locked up as Permafrost, subsurface ice reservoirs.
Term
Martian Atmosphere:
Definition
1% of the mass of Earth's.
95%C02, 3%N2, 2%Ar, less than 1%O2, high noble gas content! (thicker in past)
Term
Temp on Mars:
Definition
-170F to 50F
Term
Martian Soil:
Definition
Rich in Si and Fe, Fe oxide (rust) gives red color.
Term
The 3 Ages of Mars:
Definition
Noachian Era: first billion years, active periods of warm and wet environment, erupting volcanoes, and tectonic activity.

Hesperian Era: lasted next 500mil to 1.5 bill years, activity slowing down, plunging temps, water pooled underground caused catastrophic floods when heated (1000 Mississippi river)
Amazonian era: current age, began 2-3 bill years ago, extremely thin atmosphere.
Term
Mars Pathfinder Mission:
Definition
Warm Wet past, with thicker atmosphere
Term
Mars Global Surveyor Mission:
Definition
Surveyed and took lots of pics, measurements, plotted the terrain.
Term
Mars Odyssey Mission:
Definition
Using a gamma ra spectrometer to seach fro large quantities of frozen water, detailed maps of minerals in rocks and soils, cooling and heating (infrared camera)
Term
Galilean Satellites Properties:
Definition
1) all orbit Jupiter
2) they all are tidally locked to Jupiter
3) they all have radii larger than our Moon
4) the inner moons have densities higher than outer moons (implies that Jupiter was much warmer in the past, such that the moons formed near Jupiter have less of the volatile elements such as CO2 and H2O)
Term
Mean Densities in order of distance of the Gallilean Satellites:
Definition
Io: 3.4 (rock/ silicates)
Europa: 3.1 (rock/ silicates)
Ganymede: 1.9 (ice and rock)
Callisto: 1.8 (ice and rock)
Term
Key Stats on Io
Definition
-143 C surface temp
Thin patchy atmosphere of SO2
Active plumes (not volcanos), molten SO2
Youngest Surface (no craters)
Term
Key Stats on Europa:
Definition
Icy world, high Albedo.
Smooth surface/young and renewing
Large cracks that show ice plate tectonics
Surface is Dirty Ice Field
Term
Volume of a Shell:
Definition
4/3pi(R1^3-R2^3)
R1 is less than R2
Term
Key Stats on Ganymede:
Definition
Much less then two planets that are closer.
Very diversified surface, hinting to very active past.
Low Density=Ice Mantle 1000km thick
Ghost Craters that are smoothed by ice flow
Thin Oxygen atmosphere, with aurora's
Term
Key Stats on Callisto:
Definition
Farthest of Gallilean Satelites
Similar to Ganymede, but 10 times the craterings
Less tectonic activity, and cooler interior
Craters destroyed landscape
Term
What is Titan's Atmosphere Made of?
Definition
Methane (found using spectroscopy)
Term
Titan's Atmosphere:
Definition
1.4 times as heavy as earths, organic molecules.
Made of 90% N2, 7% CH4, 2% Ar
Term
Surface Temp of Titan:
Definition
-178C
Term
What si the triple point of methane caused by on Titan
Definition
Correct temp and pressure.
Term
what determines if a planet keeps a certain molecule?
Definition
Escape Velocity, and Temp
Term
What are the outgassing percentages of the heavy molecules?
Definition
58% H20
23%CO2
13% SO2
5% N2
Term
Temp Change as a result of greenhouse gasses on Mars, Earth, Venus:
Definition
Mars: +5 degrees
Earth: +35 degrees
Venus: +500 degrees
Term
What is the composition of a secondary atmosphere dependent on? (5)
Definition
1)distance from sun (temp)
2)Mass and Radius of Planet (surface gravity)
3)Chemical Reactions (molecules can be created or destoryed.
4)Geological activity= amount of outgassing (more=thicker)
5)Living organisms: waste products.
Term
Amount of heat stored in planets interior comes from what two sources?
Definition
1)energy of formation of the planet
2)heat generated by the decay of radioactive elements.
Term
Equation Relating Mass to Density and Volume:
Definition
M=DxV
Term
Why is it impossible for there to be a solid magnet creating the magnetic field on earth?
Definition
1) Temp exceeds the Cure Temp.
2) The Field is constantly variable.
Term
What Does the Existence of a Magnetic Field Tell us About a Planet?
Definition
1)large liquid core
2)Rich in Metals (free moving electrons)
3)Planet Has a High Rotation Rate
Term
Dipole Magnetic Field:
Definition
A magnetic field that is generated by a conductive fluid in motion.
Term
What is Chemical Fractionation?
Definition
When gravity causes heavier elements sink towards the core. (if the planet is small and cools before this can complete, it will not finish the process)
Term
Fast Cooling Rate Results in What Size Crust?
Definition
Thick
Term
For Major Terrestrial Worlds Crust Thickness is directly proportional to?
Definition
Diameter of the Planet
Term
Percentage of the total diameter, that the crust makes up on Earth/Venus, Mars, and the Moon?
Definition
.5%
1%
4%
Term
What is the Strength of a planets magnetic field determined by?
Definition
Size of Core
Rotation of Planet
Term
Why are the inner Gallilean Satellites composed of primary rocky materials while the outer ones are not?
Definition
Outgassing has drained the majority of of their icy materials, where the outer ones have had no outgassing and retain a warm core with a thick ice water mantle.
Term
Larger and thinner the core?
Definition
The more tectonic activity!
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