EAPS 105 Exam 4 Study Guide PDF

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EAPS 105, The Planets Exam 4 Study Guide From the lecture slides you should know the following: Unit 10: Moons, Tides, and Rings Evolution of the moon 1. Formation 4.5 billion years ago with magma ocean 2. Cooling of magma ocean to form lunar crust 3. Formation of the South Pole-Aitken impact basin 4. Late Heavy Bombardment forms large basins on near side 5. Volcanism fills and overflows nearside basins 6. Steadily decreasing rate of asteroid impacts through today 1. The giant impact theory of moon formation and the characteristics of a moon that would suggest it formed in this manner. Giant Impact - Prograde Orbit – started out closer to the equator, but tidal forces pushed it away. Suns gravity caused it to rotate toward the ecliptic 2. Current observations that conflict with impact theory of formation of our Moon. 3. How Mars acquired its moons Phobos and Deimos. Likely from a large asteroid impact 4. The co-accretion theory of moon formation and the characteristics of a moon that would suggest it formed in this manner. Co-accretion – moons form from an accretionary disc of dust that is thought to often surround a newly formed giant planet  Circular, prograde, and equatorial orbits.  Generally found far from the planet, since protoplanetary discs extend much farther than impact debris discs  Generally have different mineralogies, since there was no impact mixing (think gas giants) 5. How Jupiter acquired its major moons. Most likely from co-accretion 6. What controls the percentage of ice to rock in the mineralogy Jupiter’s major moons. Temperature decreases with distance from Jupiter Iceline around Jupiter (io inside and all rock) 7. The capture theory of moon formation and the characteristics of a moon that would suggest it formed in this manner. Capture: objects passing too close to a planet can be captured into orbit by its gravity.  Captured moons are identifiable by having orbits that are not aligned with the planet’s equator, are non-circular, and often retrograde  Captured moons are small and far away 8. How Jupiter acquired its small moons that orbit far from the planet. Jupiter has many small moons with orbits that are retrograde (opposite the spin of the planet), not aligned with Jupiter’s equatorial plane, elliptical, and are extremely far from the planet.  These orbital characteristics suggest these Moon were captured

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9. Pluto’s moon Charon’s likely origin. Giant Impact 10. Neptune’s moon Triton’s likely origin. Triton was likely captured from the Kyper Belt 11. What is unique about Neptune’s moon Triton. It is the only large moon in the solar system thought to be captured 12. Saturn’s moon Enceladus’ likely origin. Co-accretion 13. Evidence that our Moon formed from a giant impact.  The Moon’s chemistry is almost identical to Earth’s, suggesting mixing of the two crusts and mantles by a giant impact.  The Moon’s crust formed from the slow cooling of a magma ocean, consistent with a giant collision that caused the ejected rocks to have melted.  The Moon has very few volatiles (compounds with low boiling temperatures), consistent with them being boiled off in the heat of a giant impact.  The Moon has a very small core, consistent with only Theia’s and none of the Earth’s core being ejected into orbit. 14. What the lunar dichotomy is. The farside of the moon has relatively high topography compared to the nearside of the Moon, perhaps because of a giant impact. 15. What the Late Heavy Bombardment was. Big impact basins formed on the nearside of the Moon during a period of more numerous impacts 3.8 billion years ago known as the Late Heavy Bombardment 16. Why the South Pole-Aitken basin on the Moon is unique. The South Pole-Aitken basin in the southern hemisphere is the largest and oldest recognized impact basin. 17. The discoverer of the Galilean moons. They were first observed by Galileo Galilei in 1610 18. What is unique about Jupiter’s moon Io. Io is the most volcanically active body in the solar system 19. What is unique about Jupiter’s moon Ganymede. Ganymede is the largest in the solar system and its liquid iron outer core produces the only substantial magnetic field generated by a moon 20. What is unique about Jupiter’s moon Callisto. Despite Callisto being the size of Mercury, its internal structure has not completely differentiated —the rock, metal, and ice have not completely separated.  The lack of differentiation makes Callisto unique to all other large bodies in the Solar System 21. How a radar return signal is interpreted. If it bounces back, it implies roughness (appear bright) 22. What is unique about Saturn’s moon Titan. Titan is the only moon in the solar system that has a thick atmosphere (mostly comprised of methane  False color Cassini radar view of Titan showing very smooth radar returns what are interpreted to be liquid methane lakes —making Titan the only other body besides Earth in the solar system with liquid on its surface. 23. Why there are high tides on two sides of the Earth at the same time.  Because the Moon’s gravity elongates the Earth, similar tides occur on two sides of the Earth simultaneously 2

The Sun causes tides as well, buts its tides are smaller despite its bigger mass because it is much further away 24. What spring and neap tides are and when they occur. Spring Tide:  When the Moon and Sun tides align, high tides are highest and low tides are lowest.  These are known as “spring” tides and they occur during a new or full moon (twice each month)  Neap Tide: When the Moon and Sun tides are perpendicular, high tides are lowest and low tides are highest.  These are known as “neap” tides and they occur during first or third quarter moons (twice each month) 25. What is means for a moon to be tidally locked.  Tidal forces cause moons to become tidally locked, where one side of the moon always faces the planet  Due to tidal locking, the Moon rotates exactly once during each orbit around the Earth, meaning that the same side of the Moon (called the near side) always faces the Earth 26. That most of the major moons in the Solar System are tidally locked. Every large moon in the solar system is tidally locked Except for Hyperion due to resonance with Titan, and Pluto’s 4 outer moons due to resonances with eachother 27. That Pluto and its moon Charon are tidally locked to each other.  Pluto and Charon are tidally locked to each other and orbit about a point just above Pluto’s surface.  This results from Charon’s relatively big size compared to Pluto, which also leads both bodies to orbit about a point above Pluto’s surface 28. Why the Moon is moving away from the Earth. The Earth’s faster rotation carries the tidal bulge a little ahead of the Moon’s orbit. This causes the Moon’s orbit to speed up a little and go into a slightly higher orbit (yellow arrow).  This is causing the Moon to slowly drift away from the Earth at 4 cm/yr. 29. The fate of Mars’ moon Phobos. Mars’ rotation is slower than Phobos’ orbit, causes the tidal bulge to lag behind. As a result Phobos’ orbit is slowing down causing Phobos to slowly orbit closer to Mars.  It will eventually crash into Mars 30. Why our Moon does not experience as much tidal heating as Io.  Tidal heating occurs when moons continuously deform like an accordion  Tides always cause a moon to deform. But if that moon is tidally locked in a circular orbit, the shape of the moon remains the same as it orbits. Thus, no heat is produced.  If however, the moon is in an elliptical orbit, the tides will cause the moon to continuously change shape, which causes the interior of the moon to heat up.  Our moon remains elongated  Io has resonances with other moons, making the orbit more elliptical 31. How tidal heating effects icy moons. 

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Tidal heating may have caused the interiors of these icy moons and Pluto to melt, forming subsurface oceans 32. What the Roche limit is.  The Roche limit is the distance from a planet where tidal forces that work to rip a moon apart are equal to the moon’s gravitational forces that keep it intact. 33. What happens to a moon if it migrates inside the Roche limit.  If a moon’s orbit takes it inside the Roche limit, it will be torn apart by tidal forces  Tidal forces are stronger than the moon’s gravity, so the moon is pulled apart 34. About thick Saturn’s rings are. On average, Saturn’s rings are only ~10 m thick, orbiting on a very narrow plane aligned with Saturn’s equator. 35. Which planets have rings. Saturn, Jupiter, Uranus, and Neptune 36. The fate of Neptune’s moon Triton. Tidal forces are causing Triton to migrate toward Neptune. Eventually, it will cross the Roche limit and be ripped apart to form a spectacular ring around Neptune 37. Why Saturn’s moon Iapetus has a bulge around its equator. Saturn's moon Iapetus has a 20 km high equatorial icy ridge that is thought to be the result of a ring crashing down onto its surface.

Unit 11: Exoplanets 30. How the transit detection method works. Transit Detection method detects distant planets by measuring the minute dimming of a star as an orbiting planet passes (transits) between it and Earth

 Dimming must occur at regular intervals to indicate a planet.  Only planets whose orbits are seen edge-on can be detected 31. The method of detection used by the Kepler Spacecraft. Kepler used the transit method 32. What the time between observed exoplanet transits represents. Time it takes to complete one orbit (orbital period) 33. What a bigger drop in brightness mean for an exoplanet transit. Bigger drop in brightness means bigger planet 34. Which types of planets the transit method detects most easily. Big planets close to their stars CHECK THIS ONE 35. How the radial velocity detection method works. The radial velocity (or doppler )detection method relies on the fact that the gravitational pull of an orbiting planet will cause a star to wobble —move slightly toward the Earth (blue Doppler shift) and then slightly away (red Doppler shift) each time the planet orbits. 36. How the Doppler Effect works.  Doppler Effect: The apparent change in the frequency of a wave caused by relative motion between the source of the wave and the observer. 37. What the radial velocity method can provide that the transit method cannot. It gives us the mass of the planet 38. What the mass and volume of an exoplanet enable us to determine. Mass and volume allow us to determine its density 39. How the gravitational microlensing detection method works.

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Gravitational microlensing works the same way as a magnifying lens. Instead of glass deflecting light to make a bug look bigger, a closer star warps space to the bend light of a more distant star and it make it look bigger. • Microlensing detection method takes advantage of the way a gravitational field of a star bends the light of a more distant star, magnifying its brightness. A planet orbiting the closer star will cause a deviation in the lensing process. • Planet orbiting the closer star causes a distortion in the magnification process, like a scratch in the lens of a magnifying glass One time shot 40. The types of planets the gravitational microlensing method detects better than other methods. Planets around far away stars 41. How the direct imaging detection method works. The direct imaging detection method blocks the overwhelming glare of stars to revealing the reflected light of orbiting planets. 42. Which types of planets the direct imaging method detects better than other methods. Big planets far from their stars 43. How we can infer the chemistry of an exoplanet’s atmosphere. If passed through a prism, light spreads out into a spectrum. Missing colors show up as black lines, indicating specific gases are absorbing that part of the spectrum 44. What the absorption spectrum of sunlight passing through our atmosphere reveals about the chemistry of our atmosphere. Aliens would be able to tell that we have oxygen (O2), ozone (O3), water (H2O), and carbon dioxide (CO2) in our atmosphere. 45. Why we have so far found so few solar systems like ours. Our telecopes are not yet sensitive enough 46. The characteristics of Hot Jupiters. • Hot Jupiters are gas giants similar in size to Jupiter, but orbiting very close to their stars (well within Mercury’s orbit) and are thus very hot. • Hot Jupiters are the easiest exoplanets to detect as their large size and close orbit blocks significant sunlight and their large mass causes its parent star to wobble significantly. • Surface temperatures on the order of several thousand degrees. • Orbit their stars in a matter of days. • Probably tidally locked (one side always faces the star 47. Where Hot Jupiters probably formed. Hot Jupiters probably formed out beyond their star’s ice line, then migrated inwards due to gravitational interactions with other gas giants 48. Characteristic of hot Neptunes. Hot Neptunes are exoplanets the size of Uranus or Neptune that orbit relatively close to their stars and are thus hot compared to our ice giants 49. What is likely to happen when Ice giants migrate closer to their stars. When ice giants migrate toward their star and pass inside the ice line to become hot Neptunes, their hydrogen and helium atmospheres may boil off, leaving a gas tail like that of a comet. 50. Characteristic of lava worlds. 51. Why Mini-Neptunes are not likely to habitable.

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mini-Neptunes are large enough to have held onto hydrogen and helium atmospheres and thus would not be habitable by life as we know it, though Super-Earths might 52. What the habitable zone is. The habitable zone is the range of orbits around a star within which a rocky planet’s surface temperature is warm enough to maintain liquid water on its surface. 53. How habitable zones are influenced by star size/brightness.  A Planet too small will have trouble holding on to its atmosphere and lose its water (think Mars).  A planet too big will attract a hydrogen atmosphere (think Neptune)  The hotter a star, the farther away the habitable zone and vice-versa. Therefore, one must know the temperature of a star (based on brightness) before one can estimate where the habitable zone is located. 54. The factors considered in the calculation of an exoplanet’s Earth Similarity Index. he Earth Similarity Index (ESI) rates a planet’s potential habitability from 0 to 1 by comparing its radius, density, escape velocity, and surface temperature to that of Earth 55. What is unique about the exoplanet Teegarden’s Star b. Teegarden’s Star b is about the same size and surface temperature as Earth. It orbits a quiet (no radiation pulses) low-mass red dwarf star —small and thus lasts 10s of billions of years given lots of time for life to evolve. 56. What is unique about the exoplanet Proxima b. Proxima Centauri b, the closest potentially habitable exoplanet, is only 4 light years away  At only 4.2 light years away, Proxima b is the closest potentially habitable planet we’ll ever find.  30% bigger than Earth  Receives 30% less energy  Earth Sim. Index = 0.83 57. How we potentially detected a moon orbiting an exoplanet. 20 times larger than Jupiter with a ring system 200 times larger than Saturn’s (almost the distance of the Earth from the Sun).  A large gap in the rings may be indicate an Earth-sized moon 58. How the relative mass of the stars in a binary system influence planet orbits.  In a binary star system of similar mass, the distance of planets from the stars would vary greatly during each orbit, causing big changes in temperature probably not conducive to the evolution of life  However, if one star in a binary system has most of the mass, and orbits close to the other, planetary orbits would not look much different than a single star system, and thus a planet in this system could be habitable. 59. What a rogue planet is. Rogue planets are planets without a parent star, which happens when planets are expelled through gravitational interactions as solar systems first evolve 60. Whether it is possible to view a double sunset from a planet surface. Planets in binary star systems would have double sunrises and sunsets 61. About how many stars are estimated to be in our Milky Way galaxy. 1 billion stars 62. How many galaxies are estimated to exist.

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2 Trillion galaxies 63. How many potentially habitable Earth-like planets are out there. 2x10^20 potentially habitable planets 64. If only 1 in a billion of the estimated number of habitable planets developed life, the number of planets out there have life. 200 million Unit 12: Hazards of Space Travel 65. What killed the Apollo 1 astronauts. 1967, Apollo 1 experienced a fire during a test on the pad that killed 3 astronauts. The fire spread rapidly due to the practice of using a pure oxygen environment in the capsule. 66. What killed the Apollo 13 astronauts. After an oxygen tank blew up in route to the Moon, Apollo 13 astronauts used a gravitational assist from the Moon to successfully return home 67. Why the Space Shuttle Challenger exploded.  The program was aware of and ignored the implications of O-ring damage on numerous recovered booster hardware.  The launch took place under cold temperature conditions that had never been tested, exasperating the O-ring problem.  Managers at NASA and Morton Thiokol ignored the advice of engineers that it was not safe to launch 68. What killed the Space Shuttle Columbia astronauts. In 2003, the Space Shuttle Columbia disintegrated during reentry, killing all seven astronauts, after foam from the External Tank broke off and damaged tiles on the orbiter wing 69. The dangers of micrometeoroids. Micrometeoroids: tiny pieces of space rock (millimeters or less) traveling at very high rates of speed (measured in kilometers per second) that can cause a lot of damage. 70. What spacesuits are able to protect astronauts from. Space suits have no Radiation protection as it requires much thicker and denser material 71. What the solar wind is. The solar wind is a continuous flow of charged particles (radiation) from the sun that permeates the solar system. 72. What a solar flare is and whether it is capable of setting the Earth on fire. Solar flares are sudden, large energy releases from the Sun that carry especially high doses of radiation In the movies, solar flares are often incorrectly depicted as scorching the Earth. But we are in no danger of this happening because radiation does not ignite fires. 73. How planets are protected from radiation. Our magnetic field deflects much of the radiation from the Sun and the atmosphere absorbs most of the rest (causing the aurora lights 74. Where most cosmic rays originate from. Another source of radiation are cosmic rays, highly energetic atomic nuclei traveling through space at near light speed originating from supernovae throughout the galaxy. 75. The greatest danger to humans wishing to colonize Mars.

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Traveling to and staying on Mars will expose people to 100 times the radiation they experience on Earth, making radiation the greatest danger to humans wishing to colonize it 76. How one could live on the Moon or Mars and be protected from radiation. They should live underground 77. What the Kessler Syndrome is. The Kessler Syndrome: More collisions will create more debris which will create more collisions until the Earth may be encased in a shell of billions of pieces of orbiting debris, making it impossible for us to keep satellites in orbit (goodbye internet, cell phone service, or GPS) and no leaving the planet – forever 78. The consequences of prolonged weightlessness on the human body. Long period of weightlessness cause muscles to atrophy, bones to become brittle, the redistribution of body fluids (which effects balance, blood volume, and heart function), and other yet unknown long-term effects. 79. How one can simulate the force of gravity on a spacecraft. Weightlessness can be countered by rotating a spacecraft, generating a centrifugal force that simulates gravity. 80. How sound travels in space. Sound waves exist as vibrations in a pressured medium, such as air. There is no medium in space within which sound can travel 81. What would kill you first if you took off your helmet in space. You would suffocate It would take a...