Advice for submitting study guide answers is here. Updated through Monday, November 11.

(100)

What does it mean to say that we are communicating with extraterrestrials already? What do our signals sound like at various distances from the Earth? Explain.

(101)

Why do radio wavelengths work as the best way to communicate with potential extraterrestrials?

(102)

What is the author's response to "Fermi's question?"

(103)

What is an example of an observation Galileo made to show that objects in the Universe are not static like paintings on the inside of cathedrals?

(104)

What arguments can you make that evolution is very unlikely to result in intelligence?

(105)

How and why does the lifetime of a civilization relate to the probability that we are not alone?

The following two homework questions are from the June 2011 Scientific American article, "The Myth of Evil Aliens." You can find this article in the Content section for our course on TCU's Brightspace server.

(106)

Explain Stephen Hawking's argument regarding why we should not necessarily be attempting to contact extraterrestrials but instead simply listening. (HW)

(107)

Explain author Michael Shermer's two arguments regarding why any contact with extraterrestrial intelligence (ETI) will likely be benign. (HW)

(108)

Visit NASA Ozone Facts to learn about the Antarctic ozone hole and answer the following: From the main Ozone facts page, explain the difference between good ozone and bad ozone. (HW)

(109)

From the same NASA Ozone Facts page, under the topics menu in the top right, click on "What is the Ozone Hole?" and answer: Explain why CFC's are harmful to ozone, and explain why the ozone depletion mainly occurs over the Antarctic. (HW)

(110)

Visit the United Nations website to learn about the Montreal Protocol and explain 1-2 sentences what this protocol does. (HW)

The following four homework questions can be answered by reading the Scientific American article "Mercury: The Forgotten Planet" from the 2003 special edition on the solar system. You can find this article in the Content section for our course on TCU's Brightspace server.

(111)

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)

(112)

What is the Mercurian Grid, and how do we think it formed? (HW)

(113)

Why are craters on Mercury typically larger than craters found on the Earth's Moon? (HW)

(114)

Explain two sources of the gases in Mercury's tenuous atmosphere. (HW)

(115)

Explain how our explorations of the Martian surface may help answer questions about the origin of life on Earth. What major question are we hoping to answer and how will we answer it?

(116)

How do we know that the early Earth was hot enough to be molten (liquid) throughout?

(117)

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?

(118)

From your textbook's chapter 8.2, explain the contribution made by Alfred Wegener to our understanding of the Earth. What are two examples of evidence that supported his hypothesis about the Earth, and what was the major argument against his hypothesis, initially? (HW)

(119)

From your textbook's chapter 8.5, what is the purpose of the NASA Spaceguard survey? (HW)

The following three questions come from the August 2016 Scientific American article, "The Seven Year Mission to Fetch 60 Grams of Asteroid." You can find this article in the Content section for our course on TCU's Brightspace server.

(120)

Explain why the asteroid Bennu was selected as the target for this mission (two reasons). (HW)

(121)

One potential problem with Bennu is the unpredictability of its orbit, caused by the Yarkovsky effect. Use the diagram on pages 66 and 67 (and the description on pages 68 and 69 in the article) to explain how this effect works to change the orbit of an asteroid. (HW)

(122)

Explain the main thing we hope to learn from the sample that is returned to Earth, if all goes well. (HW)

(123)

Suppose a certain rock's current composition consists of 10 parent atoms, 220 daughter atoms, and 300 stable sibling atoms, and the radioactive parent atoms have a half-life of 5 million years. When the rock originally solidified, the number of daughter atoms was equal to half the number of stable sibling atoms. What is the solidification age of the rock? Show your work.

(124)

Explain why the Earth's surface is much younger (in terms of average solidification age) compared to the Moon's surface.

(125)

List or briefly describe the main three ways that gases can be added to a planet's atmosphere.

(126)

List or briefly describe five ways that gases can leave a planet's atmosphere.

(127)

From your textbook's chapter 9.3, explain the logic behind our conclusion (and the data from the lunar surface) that the cratering rate on the Moon and in our solar system has not been constant over time but instead there was an era of heavy bombardment during the early history of the solar system. (HW)

(128)

From your textbook's chapter 9.4, briefly describe the capture theory for the origin of Earth's Moon, then explain three problems or counterarguments the authors discuss that contradict the capture theory. (HW)

(129)

From your textbook's chapter 9.4, explain how the giant impact theory successfully explains (a) the lack of metals in the overall composition of the Moon, (b) the lack of volatiles in the Moon and (c) the similarity in composition between the Moon and Earth's crust. (HW)

(130)

From your textbook's chapter 9.5, explain how radar observations are used to determine the rotation rate of Mercury. Describe what we observe, exactly, and explain or show the difference in our observations if Mercury doesn't rotate vs rotating slowly vs rotating quickly. (HW)

(131)

From your textbook's chapter 9.5, explain why we think Mercury has such a high metal content (and high density) compared to Earth's Moon. How do we think this difference came about? (HW)

(132)

Name and briefly explain the two things necessary in a planet's interior that enable a planet to have a magnetic field.

(133)

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.

(134)

Explain why the Earth has two tidal bulges as a result of the Moon's gravity.

(135)

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.

(136)

Would we still have high tides and low tides if we had no moon? Explain.

(137)

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?

(138)

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.

Recently, the object known as Oumuamua has been in the news. To find out more about Oumuamua, read an introductory article (https://tinyurl.com/ycpkru27) and then a recent follow-up article (https://tinyurl.com/y7yts54h) and then answer the following:

(139)

What exactly is Oumuamua and why is it so unusual and newsworthy? (HW)

(140)

How do we know Oumuamua has a very elongated shape? (HW)

(141)

Why do we think Oumuamua is likely a comet, based on our theory of the origin of the solar system? What evidence in its orbit suggests that it is probably a comet? (HW)

(142)

Explain why some Astronomers have suggested Oumuamua may be artificial (alien) in origin, rather than a comet. As part of your answer, describe two observations or arguments that Astronomers have used to suggest it doesn't behave like a comet. (HW)

Read the FAQ on Meteors from the American Meteor Society and answer the following three questions:

(143)

Meteors tend to enter our atmosphere much more quickly in the early morning hours compared to evening hours. Explain why. (HW)

(144)

Why are you more likely to observe meteors after midnight compared to before midnight? (HW)

(145)

What is the radiant of a meteor shower, and how are meteor showers named? (HW)

(146)

Explain why the moon has no atmosphere.

(147)

Explain why the moon has no magnetic field.

(148)

Explain why the same face of the Moon always points at the Earth (tidal locking).

(149)

Explain the evidence that indicates Mercury has a source of internal heat, unlike Earth's moon.

(150)

Explain how Mercury's unusual orbit contributes to its tidal heating. A diagram may help.

(151)

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)

(152)

Explore the following web site from NASA's Lunar and Planetary Institute about the Martian meteorites:https://www.lpi.usra.edu/lpi/meteorites/The_Meteorite.shtml. Based on the information found here, answer the following: What conclusive evidence shows that these meteorites are from Mars? How did this meteorite get to Earth? (HW)

(153)

From your textbook's chapter 10.4, what evidence leads Astronomers to believe that the Marian volcano Olympus Mons may still be intermittently active? (HW)

(154)

From your textbook's chapter 10.5, name and explain two lines of evidence that indicate the dark streaks (or gullies) found in some steep crater walls on Mars are generated by flowing liquid water on or just beneath the surface of Mars in the present day. (HW)

(please disregard the missing numbers from 155-157)

(158)

Visit http://www.nineplanets.org/jupiter.html and answer: 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)

(159)

From your textbook's chapter 12.2, name and explain two lines of evidence that indicate there is a large ocean beneath the surface of Jupiter's moon Europa. (HW)

(160)

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 138). (HW)

The following questions are from Episode 7 of the TV Series "Cosmos: A Spacetime Odyssey," entitled "The Clean Room."

(161)

Why can't we just add up the approximate ages of sediment layers in order to deduce the total age of the Earth?

(162)

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?

(163)

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?

(164)

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?

(165)

Explain two ways in which lead harms humans at a microscopic level.

(166)

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.

(167)

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 (in other words, why we think the original atmospheres of Earth and Venus were similar).

(168)

What evidence in Venus' atmosphere tells us that the original water in the atmosphere likely did not leave the atmosphere by either condensing or through chemical reactions, going into the ground?

(169)

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.

(170)

Name and briefly explain the significance of two important differences between Venus and Earth that led Venus to undergo the Runaway Greenhouse process while Earth did not.

(171)

What evidence on the surface of Mars indicates Mars once had a thicker, warmer Earth-like atmosphere? Explain.

(172)

Explain how the loss of internal heating on Mars about 2-3 billion years ago may have led to the gradual loss of the Martian atmosphere.