INTRO ASTRONOMY: EXAM 3 STUDY GUIDE
INTRO ASTRONOMY: EXAM 3 STUDY GUIDE 10273
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This 9 page Study Guide was uploaded by Nicole Salem on Thursday February 18, 2016. The Study Guide belongs to 10273 at Texas Christian University taught by Dr. Ingram in Winter 2016. Since its upload, it has received 39 views. For similar materials see Intro Astronomy: Earth&Planets in Physics 2 at Texas Christian University.
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ASTRONOMY EXAM 3 STUDY GUIDE (103)How do we know that the early Earth was hot enough to be molten (liquid) throughout? (104)Explain the two major (gravity-related) heat sources that made the early, forming Earth so hot that it was completely molten throughout. What is the current heat source that keeps Earth's interior partially molten? (105)Suppose a certain rock's current composition consists of 30 parent atoms and 570 daughter atoms, and the parents have a half-life of 3 million years. If the original composition of the rock consisted of 480 parents and 120 daughters, what is the solidification age of the rock? Show your work. The following five homework questions can be answered by reading the Scientific American article "Mercury: The Forgotten Planet" from the 2003 special edition on the solar system. For instructions on how to electronically download pdf versions of Scientific American articles, please see Study Guide #1. (106)Explain the reasoning that leads us to believe that a large fraction of Mercury's mass consists of iron. Mercury is very dense in proportion to its size so it means that its core is made out of iron. Iron is the only element that has enough high density and abundance to be able to exist within the interior of a planet. (107)Explain why we think substantial quantities of sulfur may be present in the interior of Mercury (this has to do with its magnetic field). (HW) Because mercury has a strong magnetic field, it must have circulating molten metals in its interior. Mercury's interior is mainly made of iron, so there needs to be a chemical changing iron’s freezing point so it is a liquid even at low temperatures. Sulfur is a chemical that can do this and exists in large abundances so scientists believe that there is sulfur in mercury's core. (108)What is the Mercurian Grid, and how do we think it formed? (HW) The Mercurian Grid is a lot of linear features or a network of faults on mercury's surface. The lines run NorthSouth NortheastSouthwest. When mercury's crust solidified, mercury was rotating much faster creating an equatorial bulge. Then, when its rotation slowed down, gravity pulled mercury into a spherical shape and the shrinkage caused the grid to look like it accommodate the change. (109)Why are craters on Mercury typically larger than craters found on the Earth's Moon? (HW) The objects that hit mercury used to have higher velocities because they were closer to the sun and objects used to move faster near mercury than they did further out which created large craters. (110)Explain two sources of the gases in Mercury's tenuous atmosphere. (HW) Solar wind: strips material off of the surface and is added to the atmosphere. Some material comes from the magnetosphere when charged particles from the solar wind interact with the magnetic field. It may come from the direct in fall of comet material. The outgassing of the last original volatile substances in mercury. (111)Why can't we just add up the approximate ages of sediment layers in order to deduce the total age of the Earth? (112)How can we figure out how much lead was originally present in any given rock on the Earth, given that these rocks have changed their compositions over time due while on the Earth? (113)When Clair Patterson tried to measure the amount of lead in zircon crystals, he got wildly inconsistent results, unlike his colleague's measurements of uranium in the same crystals. What was causing the problem with Patterson's experiment? (114)Although lead is toxic and may have eventually lead to the downfall of the Roman empire, why was it used so much by the Romans? (115)Explain two ways in which lead harms humans at a microscopic level. (116)Explain how Patterson discovered that lead is not naturally abundant in the environment but instead had increased dramatically in our environment within the past hundred years or so. (117)Describe the two processes that ensure the Earth's surface remains much younger (in terms of solidification age) compared to the Moon's surface. (118)Explain why smaller planets (like Mercury and Mars) do not retain their inernal heat as long as larger planets (like Earth and Venus). (119)List or briefly describe five ways that gases can leave a planet's atmosphere. (120)Describe the main two ways that gases can be added to a planet's atmosphere. (121)Name and briefly explain the two things necessary in a planet's interior that enable a planet to have a magnetic field. (122)Explain how the Earth's magnetic field interacts with the solar wind to protect life on Earth and create the auroae visible in the atmosphere in the North and South polar regions. A diagram would really help. (123)Visit The Ozone Hole Tour to learn about the Antarctic ozone hole and answer the following: (a) How is ozone formed in the stratosphere? (b) What is the Montreal Protocol? (c) Summarize how ozone is lost (see the end of Part III) and what ingredients are present over Antarctica that allow rapid ozone loss. You do not need to detail any particular chemical reactions, just summarize what happens.(HW) (124)From chapter 4.5 of your book, answer the following: The same face (side) of the Moon always points at the Earth. We call this phenomenon "tidal locking" or "synchronous rotation". Explain why this occurs. (HW) (125)From your book's chapter 8.2, explain the evidence that tells us the Moon and Earth likely did not form together simultaneously. (HW) (126)From your book's chapter 8.2, name and briefly explain the two pieces of evidence that lead us to believe a giant impact was the origin of Earth's Moon. (HW) (127)Explain why the Earth has two tidal bulges as a result of the Moon's gravity. (128)What is the difference between spring tides and neap tides? Which type of tides should we expect to see during new moon? Full moon? 1st quarter? Explain. (129)Would we still have high tides and low tides if we had no moon? Explain. (130)What causes the Earth's tidal bulges to "lead" the Moon in its orbit? Describe this and be able to draw a simple diagram explaining this effect. How and why does this affect the rotation speed of the Earth over time? (131)Explain how the Earth's rotation, combined with the tidal bulges from the Moon, result in the Moon's orbital distance from the Earth slowly increasing over time. Diagram would really help here. (132)Briefly describe how the appearance of both the lunar Maria and the highlands. Explain how the Maria of the Moon formed and why their appearance differs from that of the lunar highlands. Maria has a smoother, dark, low elevation generally circular. Highlands’s crater is saturated bright and high elevation. Highlands has 100x more craters than Maria but Maria is younger by about .3billion years, apparently there was a period of heavy bombardment dropped right in the time frame. (133)Explain why the surface of the moon maintains a record of the era of early bombardment (the first half-billion years after the formation of the planets) while Earth's surface does not. There was no lunar atmosphere the sky is pitch black and doesn't have what it takes, low escape velocity which means the gas escapes the top of the atmosphere ; and also has no magnetic field so there is no heat which allows the solar wind to come in. (134)Explain why the moon has no atmosphere. (135)Explain why the moon has no magnetic field. (136)Read the short article from Scientific American (http://www.scientificamerican.com/article/why-are-planets-round/) on why planets are round, and explain why all of the large planets are spherical in shape. (HW) (137)Why did some observers long ago think that Venus has a moon? What was the hypothetical "Neith" as it relates to Venus? What is the currently accepted explanation of "observations" of Venus' moon? (The Nine Planets website is a good place to go for this, look under the heading "Hypothetical Planets") (HW) (138)Read http://www.physics.upenn.edu/nineplanets/venus.html and briefly explain why no small craters exist on Venus. (HW) (139)Read this article and describe the evidence that Mars may have once experienced plate tectonics just like the Earth. Specifically, describe what the evidence is, exactly, then explain why that evidence points to the existence of a magnetic field (describe how a magnetic field helps create such a feature in the rocks). For more on this magnetic phenomenon, including a helpful diagram, you can read the Wikipedia article on plate tectonics. (HW) Just like on earth there are patterns of magnetic stripping on mars. Strips are formed by seafloor spreading which requires plate tectonics. The iron bearing minerals in the strips align in the same direction. They align because when the new magma hardens the minerals magnetize and freeze in the direction of the magnetic field. This alignment shows evidence of a magnetic field. (140)Explain the evidence that indicates Mercury has a source of internal heat, unlike Earth's moon. (141)Explain how Mercury's unusual orbit contributes to its tidal heating. A diagram may help. Mercury has tidal heating because of its orbit and rotation. It makes one and a half rotations per orbit. The orbit is elliptical, so every time Mercury is close to the Sun on its orbital path, the long axis points toward the Sun. When mercury is furthest away from the sun on its orbital path, the long axis is still pointed away from the Sun. The Sun's gravitational pull on Mercury's elliptical body leads to compression and stretching that depends on its location in orbit. This causes Mercury to have internal heating and a magnetic field. (142)Why doesn't Venus have a magnetic field? Explain. Because it doesn't rotate and has plenty of internal heat (143) Explain the properties of the surface of Venus leads us to the conclusion that (a) the solidification age of the surface is about 500 million years old (about 5x that of Earth's surface) and (b) that at that time 500 million years ago, Venus probably suffered some sort of sudden event that caused the whole planet to melt and the whole surface to reset itself. a. Venus crater density is about 5x Earth's.. Venus' craters are uniformly distributed. Venus' craters are pristine due to lack of weathering. Earth's average solidification age is 100 million years while Venus' is 500 million years. We know that it was sudden because there is nothing that could slowly erase the craters like weathering. We also know that it affected the entire planet because the craters are uniformly distributed. (144) Explain why the abundance of Argon in the atmospheres of Earth and Venus remain constant over billions of years (talk about how it avoids each possible "sink"), unlike other gases like methane, water vapor and carbon dioxide. (145) One possible explanation for the lack of water on Venus is that Venus never had much water to begin with, compared to the Earth. Explain two reasons why this explanation is not plausible. (146) Explore the following web site from NASA's Goddard Space Flight Center about the Martian meteorites:http://rsd.gsfc.nasa.gov/marslife/marsmet/. Based on the information found here, answer the following: What conclusive evidence shows that these meteorites are from Mars? Why aren't these meteorites red like the Martian surface soil? (HW) Meteorites are much younger than the typical meteorite and asteroids. They contain a higher amount of volatiles than normally. Finally gasses trapped in them match the gases that are in Mars's atmosphere. The real color on mars comes from oxidized iron from weathering. None of these meteorites have been weathered. The following five questions come from the Scientific American article "Mars in Motion" (May 2013 issue). Please see study guide #1 for instructions on how to download Scientific American articles from the TCU library website. These five questions also appeared in Lab #8 - "Planet Four". (147) Describe the evidence observed by the Mars Global Surveyor in 2000 and 2006 that led scientists to believe running water may exist on Mars currently. (HW) The MGS identified that Mars had surface features resembles gullies carved by water. The, in 2006, the MGS showed that lightcolored material had spilled out of the gullies (148) Explain two related pieces of evidence collected by the HiRISE camera that indicates the gullies first seen by the Mars Global Surveyor are more likely related to Carbon Dioxide that liquid water flow.(HW) The gullies formed on patterns, which matches the seasonal distribution of carbon dioxide frost. Also, when dry ice coats the ground, the surface and atmospheric temperatures stabilize at the carbon dioxide's frost point, not waters freezing point indicating they are more likely related to carbon dioxide. (149) According to the diagram on page 63 of the article (page 6 of the pdf), why does the Southern hemisphere of Mars experience warmer summers compared to the Northern hemisphere? From the textbook's section 2.2 (pages 36-37 specifically), explain why Earth does not behave similarly to Mars. (HW) Because of Mars' elliptical orbit, its perihelion is much closer to the sun. This phase happens during the summers in the Southern hemispheres and this creates more extreme seasons. Unlike Mars, this does not happen on Earth because the southern hemisphere has a big part covered by ocean water, which is harder to heat and cool. (150) Explain two pieces of evidence that led the author to believe the dark lines seen by the HiRISE camera, the Recurring Slope Lineae (RSL), were caused by intermittently flowing liquid water. (HW) 1. We are finding these RSL in areas where Mars in warmest where water should not have been flowing. 2. Peak RSL corresponds to temperatures in the shallow subsurface, which happens months later than peak surface heating. (151) Name and briefly explain the two things limit the ability of the Mars Reconnaissance Orbiter (MRO) to directly identify actual flowing water on the surface? (HW) 1. The MRO may not have the necessary spatial resolution to pinpoint narrow stripes across the surface. 2. The MRO's orbit allows the orbiter to take pictures during Mars' afternoons, when water is either not present or abundant. (152) From Chapter 12.2, briefly explain the origin of the Oort Cloud and explain why it has a spherical shape. Also explain the origin of the Kuiper Belt and why its shape is more like a disk. (HW) (153) From Chapter 12.4, explain why the presence of unusually high amounts of iridium in the boundary layer from 65 million years ago led scientists to believe a large impact occurred at that time on Earth. Also list three other pieces of evidence in support of this hypothesis of a large impact. (HW) (154) From Chapter 12.4, first summarize the argument made in the book that the presence of jovian planets in our solar system has made it easier for life to exist on the Earth. Second, summarize the argument that even though Jupiter may have made it easier for life to exist on Earth, it also slowed down the evolutionary process. (HW) (155) Read the FAQ on Meteors from the American Meteor Society and answer the following: (a) Meteors tend to enter our atmosphere much more quickly in the early morning hours compared to evening hours. Explain why. (b) Why are you more likely to observe meteors after midnight compared to before midnight? (c) What is the radiant of a meteor shower, and how are meteor showers named? (156) More from the FAQ on Meteors: (a) Observers tend to see more meteors per hour when the radiant is higher up in the sky instead of just rising or very low. Explain why (2 reasons). (b) What is ZHR and why is your observed number of meteors per hour likely to be much less than this? (c) What causes a meteor storm as opposed to a meteor shower? (d) Are meteor storms dangerous to observers? Explain why or why not. (157) What is Deuterium? What is heavy water? One explanation for the lack of water on Venus is that the water was absorbed into the crust somehow and now resides below the surface in aquifers or underground lakes. Explain how the heavy/light water ratio tends to argue against this hypothesis. Deuterium is heavy hydrogen. Heavy water is enriched and differentiation makes the heavy water gather near the bottom. Earth is 1/1000 heavy water where Venus is 1/50, that means its 20x more common to have heavy water, water vapor would say that it went through the ground but it didn't because of the ratio of heavy water so it must have gone through the top (158) Although Venus started with an atmosphere that was probably very similar in mass and composition compared with the Earth, various differences between Earth and Venus led to a gradual loss of water vapor on Venus, combined with an enormous increase in the carbon dioxide content. Describe the positive feedback mechanism (Runaway Greenhouse Effect) by which water is lost and the atmosphere thickened. There was more water vapor in the atmosphere because it became warmer. Water vapor is easier to lose because of the lack of a magnetic field and solar wind stripping. Since the water vapor was lost, there was more room for carbon dioxide. The more carbon dioxide, the warmer it gets. If it gets warmer there is more water vapor and then the cycle continues. Also there is no ozone layer. The ultraviolet rays are broken up which results in less water in the atmosphere. (159) Name and briefly explain the significance of three important differences between Venus and Earth that led Venus to undergo the Runaway Greenhouse process while Earth did not. (160) Briefly explain two lines of evidence that indicate Mars has little significant internal heat. (161) What evidence on the surface of Mars indicates Mars once had a thicker, warmer Earth-like atmosphere? Explain. (162) Explain what "dynamical heating" is and how Jupiter is likely responsible for the formation of the asteroid belt and also the relatively small size of Mars. The following two homework questions are from the June 2011 Scientific American article, "The Myth of Evil Aliens." (163) Explain Stephen Hawking's argument regarding why we should not necessarily be attempting to contact extraterrestrials but instead simply listening. (HW) (164) Explain author Michael Shermer's two arguments regarding why any contact with extraterrestrial intelligence (ETI) will likely be benign. (HW) (165) Visit http://www.nineplanets.org/jupiter.html and describe what is thought to be the main source of Jupiter's internal heat. (HW) (166) From the same web site mentioned above, what is the origin of Jupiter's faint ring system? In other words, where do the rocky particles come from that make up this thin, dark ring? (HW) (167) Seen here and explained more fully here are the aurorae on Jupiter. What is the origin of the auroral ovals, streaks and dots on Jupiter? (HW) (168) From the February 2013 Scientific American (short) article, "Ring Theory," answer the following: According to the researchers in the article, what is the likely origin of the systems of satellites surrounding Saturn, Uranus and Neptune? (HW) The following three questions are from the March 2010 Scientific American article, "The Moon That Would Be a Planet," about the recent discoveries on Saturn's moon, Titan. (169) Explain why planetary scientists, prior to the Huygens encounter with Titan, believed that Titan may have a methane cycle similar to the water cycle we have here on Earth. (HW) (170) What evidence tells us that methane "rain" may be falling at times on Titan? (HW) (171) Name and briefly explain two pieces of evidence that Titan has ongoing volcanism on its surface. (HW) (172) Visit http://zebu.uoregon.edu/disted/ph121/js21.html in order to learn about the color differences between the gas giants. In particular, explain why Jupiter and Saturn have an orange-red color while Neptune and Uranus have a blue-green color. (HW) (173) Visit http://nineplanets.org/triton.html to learn about Neptune's largest moon, Triton, and answer: What makes Astronomers think that Triton is a captured moon? Why is Triton gradually moving closer to Neptune (for hints on this, see your answer to 109). (HW) (174) Read the story about the discovery of the planet Neptune here and answer the following: Explain how Neptune was first discovered, and explain later why credit for the discovery was shared between the Frenchman Le Verrier and the Englishman Adams. (HW) (175) What are the Kirkwood gaps? Explain how they are formed. As part of your answer, address the following: Why would an asteroid in one of the gaps be affected so radically by Jupiter while an asteroid just to one side or the other of a gap isn't affected? (176) Explain how the gap in Saturn's rings, known as the Cassini Division, is formed. (177) What is the Roche Limit? Explain why the debris that makes up Saturn's rings doesn't coalesce to form a moon. (178) How do we know that Saturn hasn't always had a ring system? Explain the process by which we think Saturn acquired a ring system. (179)Although Io is similar in many ways to Earth's Moon, it orbits much more quickly around Jupiter (once every 40 hours as opposed to the Moon's 27.3 day sidereal period). Use the equation of orbital velocity to help explain why. (180)Why did Astronomers expect Io to be cold and lifeless, with little geological activity, like the Moon, prior to the first images taken by the Voyager I spacecraft. (181)Explain the source of heating that keeps Jupiter's moon Io so volcanically active. (182)Explain what provides the energy the keep Io's orbit elliptical (higher energy orbit) instead of circular (lower energy orbit). (183)Explain the origin of Io's plasma torus. (184)Explain the evidence that indicates Europa has liquid water beneath its icy crust.
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