Physics 20073 - Study Guide #4

Updated through Thursday, July 31. Current study questions can be found here.

(140)
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.

(141)
Why do radio wavelengths work as the best way to communicate with potential extraterrestrials?

(142)
What is the Fermi paradox, and what is one possible response?

(143)
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?

(144)
What arguments can you make that evolution is very unlikely to result in intelligence? What is an emergent property? Explain this concept in general, and then give one example.

(145)
How and why does the lifetime of a civilization relate to the probability that we are not alone?

(146)
Two of the most easily recognizable constellations that are up in the sky at this time of year are Lyra and Aquila. Find the following information about these constellations:

This is pretty easy to find on the web. A good place to go for mythology is http://www.emufarm.org/~cmbell/myth/myth.html, but remember to keep your summary fairly short so it is easy to remember the most important parts. A good place to go for simple star charts is http://www.dibonsmith.com/constel.htm. For star names and other information, try http://www.astro.wisc.edu/~dolan/constellations/. (TQ)

(147)
Read the article at http://www.nineplanets.org/hypo.html#neith and answer the following: 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? (TQ)

(148)
Read http://www.nineplanets.org/venus.html and briefly explain why no small craters exist on Venus. (TQ)

(149)
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). (TQ)

(150)
The NASA spacecraft "Mars Odyssey" has recently completed its mission to study the Martian surface and atmosphere. Visit the website of Mars Odyssey (look under "Science" and "Detailed Objectives") at http://mars.jpl.nasa.gov/odyssey/index.html and answer the following: How were we able to recognize where water is beneath the surface on Mars? Explain how that observation is made.(TQ)

(151)
Explore the following web site from NASA's Goddard Space Flight Center about the Martian meteorites:http://www-curator.jsc.nasa.gov/antmet/marsmets/index.cfm. 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? (TQ)

(152)
The sky on Mars has a butterscotch color, instead of the blue color of the sky on Earth. Read the following article from NASA about atmospheric color:http://webexhibits.org/causesofcolor/14C.html. Explain in 1-2 sentences what gives the Earth's atmosphere its blue color. Next, briefly explain the one significant difference between Earth's and Mars' atmosphere that gives Mars its color (without this difference, Mars' sky would look blue like Earth's). (TQ)

(153)
From the Wikipedia page on Ceres answer the following: Who discovered Ceres? Ceres itself accounts for about what fraction of the combined mass of all the asteroids, which in total are about 4% of the moon's mass? In September 2007, NASA launched a spacecraft to study Ceres. What is it called, and what is the other asteroid it will visit? (TQ)

(154)
Based on information from the New Horizons Pluto Mission web page at http://www.pluto.jhuapl.edu/science/everything_pluto/7_atmosphere.html, find out about how we discovered Pluto's atmosphere and explain it simply in 1-2 sentences (with a sketch of the data). What is Pluto's atmosphere primarily made of? (TQ)

(155)
What are the Trojan asteroids? Where are they found in the solar system? How do they remain in such an unusual orbit? (TQ)

(156)
Visit http://www.nineplanets.org/jupiter.html and describe what is thought to be the main source of Jupiter's internal heat. (TQ)

(157)
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? (TQ)

(158)
Seen here are the aurorae on Jupiter. What is the origin of the auroral ovals, streaks and dots on Jupiter? You may need to follow some of the links on that page for a more complete answer. (TQ)

(159)
Visit NASA's Galileo mission web site at http://www.jpl.nasa.gov/galileo/ and use the information gained from the web site to answer the following: Three of Jupiter's four large moons (Europa, Ganymede and Callisto) show very faint traces of an Oxygen atmosphere. What is believed to be the source of this Oxygen (it isn't biological, apparently)? The site is extensive, so you may find it helpful to utilize the search engine in the sidebar there to find what you need.(TQ)

(160)
From the same web site, answer the following: Which of Jupiter's moons has a strong, detectable magnetic field of its own? How was it discovered? What is the source of the magnetic field? (TQ)

(161)
Which of Saturn's moons is thought to responsible for Saturn's E-ring? Explain how we think the E-ring formed and how it may be replenished (particles in the E-ring don't last very long). You can find information about Saturn's moons and the other questions that follow either online or in your textbook. (TQ)

(162)
What are shepherd moons, and how are they related to Saturn's F ring? (TQ)

(163)
Some icy satellites, like Iapetus, Rhea and Dione, have a different albedo (reflectively) on each hemisphere. In other words, they are bright on one side and dark on the other. What is thought to be the cause of this strange coloration? (TQ)

The next four thought questions are from a series of SETI-related articles found at the Sky and Telescope magazine website: http://skytonight.com/resources/seti

(164)
From the article "SETI Searches Today": Why is the band of frequencies between 0.5 and 60 Gigahertz the best part of the radio spectrum in which to search for signals? This is answered on the first page. (TQ)

(165)
From the article "SETI Searches Today": What are two reasons to search for SETI signals near the 21-cm wavelength at which Hydrogen atoms naturally emit light? (TQ)

(166)
From the article "Smarter SETI Strategy": Why do the authors think that SETI signals are likely to come from a few very powerful sources (detectable easily with all-sky surveys) rather than from lots of faint sources (detectable with targeted, very sensitive surveys)? This is answered more clearly on the 2nd page of the article. (TQ)

(167)
From the article "A Big New Step in the Search for ET": Describe two arguments in favor of Optical SETI searches and why other civilizations might try to use optical wavelengths instead of radio to communicate with us. (TQ)

(168)
Why does Venus lack a magnetic field?

(169)
Explain how the craters on Venus differ from craters found on Earth in two parts: First, explain how we use the concept of Crater Retention Age to estimate the solidification age of Venus' surface to be about 500 million years. Second, craters on Venus all tend to have a pristine appearance compared to craters on the Earth. Explain why this difference exists.

(170)
Explain the evidence that implies Venus suffered some sort of catastrophic event about 500 million years ago that essentially resurfaced the planet.

(171)
Describe the mechanism (besides giant impact) that may have resulted in this resurfacing of Venus referred to in question 170 (melting cycle).

(172)
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.

(173)
If Venus had twice as much Argon today as the Earth, what would we then assume about Venus' original atmosphere? Explain.

(174)
Name and briefly explain the significance of three important differences between Venus and the Earth that led Venus to undergo the Runaway Greenhouse process while Earth did not.

(175)
What is Deuterium? What is heavy water? What is the difference between heavy water and normal water? An alternative 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.

(176)
Why do we think Mars has little significant internal heating (compared to Earth and Venus)? Why doesn't Mars have a significant magnetic field?

(177)
Name and briefly explain two reasons why Olympus Mons on Mars is so much larger than any mountain on the Earth.

(178)
Explain the mechanism behind the global dust storms that periodically cover the Martian surface. Why don't similar storms happen on Earth?

(179)
Name and explain the physical, observed evidence that tells us Mars once had an Earthlike atmosphere at some point in its past.

(180)
The Martian atmosphere today has about 1% of the mass of Earth's atmosphere. Explain how Argon reconstruction seems to imply the original mass of the Martian atmosphere was also about 1% of the mass of the Earth's atmosphere.

(181)
How does the Argon isotope ratio on Mars compare to Earth? Why does this ratio argue that Argon reconstruction is probably not correct to apply on Mars as in question 180?

(182)
Explain the "freeze out" theory that may have led to the loss of the Martian atmosphere. Specifically, explain what triggered the beginning of this process and how this process gradually leads to a colder atmosphere which causes the water to condense into solid ice on (or under) the surface (the "freezing out" part).

(183)
Explain the evidence related to Argon that tends to refute the "freeze out" theory (I will review this on Wednesday).

(184)
How does the "giant impact" theory propose to explain the loss of the Martian atmosphere? Explain the evidence on Mars that contradicts the giant impact theory.

(185)
How does the "impact erosion" (IE) theory propose to explain the loss of the Martian atmosphere? Why does the IE process occur on Mars and not on Earth, according to the theory (two reasons)?

(186)
How does the "sputtering" theory propose to explain the loss of the Martian atmosphere? Why does Mars presumably suffer from this effect while Earth does not?

(187)
Initial soil tests from the Viking lander seemed to indicate the presence of life on Mars. Describe the control experiment used to show that these initial positive results were probably false.

(188)
Explain what "dynamic heating" is and how Jupiter is likely responsible for the formation of the asteroid belt and also the relatively small size of Mars.

(189)
What are the Kirkwood gaps? Explain their origin. 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?

(190)
Explain what comets are, then describe and explain the behavior of both the gas (plasma) and dust tail.

(191)
Explain the origin of meteor showers. Why do meteor showers occur at the same times each year?

(192)
What is the radiant of a meteor shower? Explain how meteor showers are named.

(193)
Use a simple diagram of the Earth and its orbit around the Sun (a top view) to help explain why the best time to observe a meteor shower is in the few hours before dawn.

(194)
What is the KT boundary? We know a mass extinction happened at around that time. Name and briefly explain two pieces of evidence that indicate an impact was likely the cause.

(195)
Why is Jupiter's magnetic field so much stronger than Earth's? As part of your answer, explain why much of the Hydrogen in Jupiter is in liquid or molten form (in which it behaves like a metal).

(196)
Explain the origin of the belts and zones on the visible surface of Jupiter.

(197)
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.

(198)
Although Io has about the same size and (roughly) the same composition as Earth's Moon, Io is incredibly active geologically. Explain what causes this (two related processes).

(199)
What is the origin of the plasma (plasma just means hot, ionized gas) torus that marks out the path of Io's orbit?

(200)
What makes the surface of Europa so young (such a low crater density, bright coloring)? What causes the cracks in its surface?

(201)
Explain why we think Europa is one of the most likely objects in the solar system besides Earth to have life as we know it.

(202)
Ganymede is covered with ice, like Europa, but it has regions that appear relatively dark and light. How and why does the solidification age of a darker region typically compare to the age of a lighter region on icy moons?

(203)
What observational evidence tells us that the rings of Saturn are made up of millions of tiny independently orbiting particles rather than a solid sheet of matter? Explain. As part of your answer, describe (or show) what the evidence would look like if Saturn's rings were a solid sheet of matter.

(204)
Explain how Mimas creates the resonance gap in Saturn's ring system known as the Cassini Division.

(205)
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 (as part of your answer, explain what the Roche Limit is).