Exam 3 ExpectationsExam 3 ContentMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsMust KnowsExam 3Must KnowsMust KnowsMust KnosMust KnowsMust KnowsMust KnowsMust Knows – If I get to rings on FridayMust Knows – If I get to rings on FridayMust Knows – If I get to rings on FridayMust Knows – If I get to rings on FridayMust KnowsEXAM 3 EXPECTATIONSA Guide to what you need to knowExam 3 Content•Exam 3 will cover Chapter 8: Moon Formation & Evolution + MercuryChapter 9: VenusChapter 10: MarsChapter 11: JupiterChapter 12: Saturn (up to Friday, 18 Nov. Lecture)•Exam 3 structure:105 Points on Exam: Top score: 105% –Multiple-choice–Fill-in-the-Blank–Concept Questions (Short Answer)•There will be bonus questions (worth 5 pts total)=> Max score possible: 105+5 = 110%What and how much of whatMust Knows•Know the Four Moon formation hypotheses, and why Giant Impact is favored:1. Coformation (Sister) Theory: Moon and Earth formed together. FAILS because in this case the Moon should have a similar composition to Earth, e.g., The Moon should have a significant iron core2. Fission (Daughter) Theory: While molten, the Earth spun really fast and spun-off the Moon. Explains composition similar to Earth’s Mantle, but FAILS because why would the Earth be spinning that fast?Chapter 8: Moon Formation partMust Knows•Know the Four Moon formation hypotheses, and why Giant Impact is favored:3. Capture Theory: Moon and Earth formed separately in different parts of the disk (hence different composition), and the Earth captured the Moon. FAILS because nearly impossible for the Earth to capture a moon-sized object4. Giant Impact Theory (favored theory): The early, already differentiated Earth, experience a giant impact with a Mars-sized protoplanet (named Theia) at a glancing blow that stripped off mantle material that became the Moon. THE PHYSICS ALLOWS THIS!Chapter 8: Moon formation partMust Knows•Know that planetary scientists think that the original surface of the Moon was a global lunar magma ocean that was melted via repeated impacts.Formation of the Maria:–Crust formed and later, during the Late Heavy Bombardment, the very large impact basins (very big craters) were filled with the magma underneath the thin near-side crust forming large, roughly circular smooth areas that were enriched in iron (hence darker in color). These lava-filled basins became the maria–Maria are these very large, ancient, magma-flooded impact basins–Maria appear on the Lunar Near-side because crust is thinner than it is on the Lunar Far-side•Giving rise to the Near-side Far-side dichotomy, i.e. the face we see nearly all the maria on the near-side, while the far-side is almost entirely cratered highland terrain.Chapter 8: Moon Evolution PartMust KnowsChapter 8: Mercury•1st Planet from the Sun•Due to it’s proximity to the Sun and having an orbit interior to Earth’s, Mercury always appears close to the Sun.–Maximum angular distance: 28o–This occurs when Mercury is at greatest elongation (largest angle you can draw between Earth-Sun line and Mercury, or Venus, if you are considering that planet).•Mercury has a 3:2 spin-orbit resonance–Know what a spin-orbit resonance is. That is, if I give you that Planet Memptine has a 7:5 spin-orbit resonance, you can tell me that Planet Memptine rotates about its axis SEVEN times for every FIVE times it orbits its star.Must KnowsChapter 8: Mercury•Know that Mercury has no permanent atmosphere.•Know that Mercury does have a global magnetic field that is likely created by the dynamo effect, but is 1% that of Earth’s.–How Mercury is able to generate a mag. field having such a slow rotation rate is a current area of research helping us understand how planetary dynamos actually operate. Likely, the slow rotation is compensated for by the absolutely enormous (85% of the radius) iron core.•Know that water-ice has been found, surprisingly, on both the Moon and Mercury in the dark depths of the permanently shadowed craters at the poles. –Permanently shadowed because of almost no axial tilt•Know that Mercury has the largest iron core of the terrestrial planets relative to planet size (85% of its radius)Must KnowsChapter 8: Mercury•Know the major surface features of Mercury–Large-scale topography: Covered with impact craters with smooth intercrater plains between the craters.–Major surface feature: Caloris Basin – a very large (1400 km) ancient impact basin that has an associated “weird” terrain on the direct opposite side (antipodal… just a cool word) of Mercury–Unique to Mercury: Mercury is the only planet to have step-walled pits, called hollows, that are found exclusively on crater floors and crater rims.–Mercury has several 100 km long, tall (few km), cliffs called scarps and given names of [Something] Rupes that formed as a result of Mercury significantly cooling in its interior (due to small size) and shrinking. The shrinking squeezed the crust resulting in the scarps.•We see scarps on the Moon as well that are formed by the same process. However, the Moon’s scarps, however, are much smaller and indicate a smaller amount of shrinkage.Must Knows•Mars’s relative small size (small baked potato) compared to Earth implies that it has cooled to the point where it can no longer support a planetary dynamo and generate a mag. field.•Venus’s similar size to Earth indicates that it should have an internal structure similar to Earth… molten metallic core; convective mantle (but no plate tectonics)–However, very slow rotation rate of -243 days (retrograde rotation… backwards compared to the other planets and expectation based on nebular theory) is too slow to support a planetary dynamo, and hence no magnetic field for VenusGeneral Comparative PlanetologyMust Knows•Know how we use Real vs. Expected Temperatures for terrestrial planets and gas giant planets to infer different information:–Terrestrial planets: Real Temp. > Expected temp implies the greenhouse effect caused by greenhouse gases and therefore has an atmosphere [Exam 2 material]–Gas giant planets: Real Temp. > Expected Temp. implies that the planet is
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