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< \setcounter{figure}{0}
< \setcounter{table}{0}
< \setcounter{equation}{0}
< \hspace*{3.0in}Name:{\hrulefill} \\
< \hspace*{3.25in}Date:{\hrulefill}
< 
< \begin{Large}
< \section{\bf Introduction to the Geology of the Terrestrial Planets}
< \end{Large}
< 
< \subsection{Introduction}
< 
< There are two main families of planets in our solar system: the Terrestrial
< planets (Earth, Mercury, Venus, and Mars), and the Jovian Planets (Jupiter,
< Saturn, Uranus, and Neptune). The terrestrial planets are rocky planets
< that have properties similar to that of the Earth. While the Jovian planets
< are giant balls of gas. Table \ref{table:pproperties} summarizes the main properties of the
< planets in our solar system (Pluto is an oddball planet that does not fall into either
< categories, sharing many properties with the ``Kuiper belt'' objects discussed
< in the ``Comet Lab'').\\
<  
< \begin{table}[ht]
< \caption{The Properties of the Planets}
< \begin{center}
< \begin{tabular}{|c|c|c|c|}\hline
< Planet & Mass & Radius & Density\\
< ~ ~ ~  & (Earth Masses) & (Earth Radii) & gm/cm$^{\rm 3}$\\
< \hline
< Mercury& 0.055 & 0.38 & 5.5\\
< \hline
< Venus & 0.815 & 0.95 & 5.2 \\
< \hline
< Earth & 1.000 & 1.00 & 5.5\\
< \hline
< Mars  & 0.107 & 0.53 & 3.9\\
< \hline
< Jupiter& 318 & 10.8 & 1.4\\
< \hline
< Saturn & 95  & 9.0 & 0.7\\
< \hline
< Uranus & 14.5 & 3.93 & 1.3\\
< \hline
< Neptune & 17.2& 3.87 & 1.6\\
< \hline
< Pluto & 0.002 & 0.178 & 2.1 \\
< \hline
< \end{tabular}
< \end{center}
< \label{table:pproperties}
< \end{table}
< 
< It is clear from Table \ref{table:pproperties} that the nine planets in our solar system span
< a considerable range in sizes and masses. For example, the Earth has 18
< times the mass of Mercury, while Jupiter has 318 times the mass of the
< Earth. But the separation of the planets into Terrestrial and Jovian is
< not based on their masses or physical sizes, it is based on their densities (the
< last column in the table). What is density? Density is simply the mass of an 
< object divided by its volume: M/V. In the metric system, the density of
< water is set to 1.00 gm/cm$^{\rm 3}$. Densities for some materials you are 
< familiar with can be found in Table \ref{table:densities}.\\
< 
< \begin{table}
< \caption{The Densities of Common Materials}
< \begin{center}
< \begin{tabular}{|c|c|c|c|}\hline
< Element or & Density & Element & Density\\
< Molecule  & gm/cm$^{\rm 3}$ &~ ~ & gm/cm$^{\rm 3}$\\
< \hline
< Water& 1.0 & Carbon & 2.3\\
< \hline
< Aluminum & 2.7 & Silicon & 2.3 \\
< \hline
< Iron & 7.9 & Lead & 11.3\\
< \hline
< Gold  & 19.3 & Uranium & 19.1\\
< \hline
< \end{tabular}
< \end{center}
< \label{table:densities}
< \end{table}
< 
< If we examine the first table we see that the terrestrial planets all
< have higher densities than the Jovian planets. Mercury, Venus and Earth
< have densities above 5 gm/cm$^{\rm 3}$, while Mars has a slightly lower
< density ($\sim$ 4 gm/cm$^{\rm 3}$). The Jovian planets have densities
< very close to that of water--in fact, the mean density of Saturn is lower
< than that of water! The density of a planet gives us clues about its
< composition. If we look at the table of densities for common materials, we see 
< that the mean densities of the terrestrial planets are about halfway between 
< those of silicon 
< and iron. Both of these elements are highly abundant throughout the Earth, and
< thus we can postulate that the terrestrial planets are mostly composed
< of iron, silicon, with additional elements like carbon, oxygen, aluminum 
< and magnesium. The Jovian planets, however, must be mostly composed of
< lighter elements, such as hydrogen and helium. In fact, the Jovian
< planets have similar densities to that of the Sun: 1.4 gm/cm$^{\rm 3}$.
< The Sun is 70\% hydrogen, and 28\% helium. Except for small, rocky cores, the
< Jovian planets are almost nothing but hydrogen and helium.\\
< 
< The terrestrial planets share other properties, for example they all rotate
< much more slowly than the Jovian planets. They also have much thinner
< atmospheres than the Jovian planets (which are almost {\it all} atmosphere!).
< Today we want to investigate the geologies of the terrestrial planets to
< see if we can find other similarities, or identify interesting differences.
< 
< \subsection{Topographic Map Projections}
< 
< In the first part of this lab we will take a look at images and maps of
< the surfaces of the terrestrial planets for comparison. But before we do so,
< we must talk about what you will be viewing, and how these maps/images
< were produced. As you probably know, 75\% of the Earth's surface is covered by 
< oceans, thus
< a picture of the Earth from space does not show very much of the actual
< rocky surface (the ``crust'' of the Earth). With modern techniques (sonar,
< radar, etc.) it is possible to reconstruct the true shape and structure
< of a planet's rocky surface, whether it is covered in water, or by very
< thick clouds (as is the case for Venus). Such maps of the ``relief'' of the 
< surface of a planet are called {\it topographic} maps. These maps usually color
< code, or have contours, showing the highs and lows of the surface elevations.
< Regions of constant elevation above (or below) sea level all will have the
< same color. This way, large structures such as mountain ranges, or ocean 
< basins, stand out very clearly.\\
< 
< There are several ways to present topographic maps, and you will see two
< versions today. One type of map is an attempt at a 3D
< {\it visualization} that keeps the relative sizes of the continents in
< correct proportion (see Figure \ref{figsphthreeD}, below). But such maps only allow you to see a small
< part of a spherical planet in any one plot. More commonly, the entire
< surface of the planet is presented as a rectangular map as shown in
< Figure \ref{figtopo}. Because the
< surface of a sphere cannot be properly represented as a rectangle, the
< regions near the north and south poles of a planet end up being highly 
< distorted in this kind of map. So keep this in mind as you work through
< the exercises in this lab.
< 
< \begin{figure}[ht]
< \centerline{{\includegraphics[width=5cm]{Terrestrial/usearth.jpg}}}
< \caption{A topographic map showing one hemisphere of Earth centered on North
< America. In this 3D representation the continents are correctly rendered.}
< \label{figsphthreeD}
< \end{figure}
< 
< \begin{figure}[ht]
< \centerline{{\includegraphics[width=6cm]{Terrestrial/globalrelief.jpg}}}
< \caption{A topographic map showing the entire surface of the Earth.
< In this 2D representation, the continents are incorrectly rendered. Note
< that Antarctica (the land mass that spans the bottom border of this map)
< is 50\% smaller than North America, but here appears massive. You might
< also be able to compare
< the size of Greenland on this map, to that of the previous map.}
< \label{figtopo}
< \end{figure}
< 
< \subsection{Global Comparisons}
< 
< In the first part of this lab exercise, you will look at the planets 
< in a {\it global} sense, by comparing the largest structures on the 
< terrestrial planets.  Note that Mercury has recently been visited by
< the Messenger spacecraft. Much new data has recently become available, but
< we do not yet have the same type of plots for Mercury as we do for the other
< planets.
< ~ ~\\
< \begin{flushleft}
< {\bf Exercise \#1}: At station \#1 you will find images of Mercury, Venus,
< the Earth, the Moon, and Mars. The images for Mercury, Venus and the Earth
< and Moon are in a ``false color'' to help emphasize different types of
< rocks or large-scale structures. The image of Mars, however, is in ``true 
< color''.
< \end{flushleft}
< ~ ~\\
< Impact craters can come in a variety of
< sizes, from tiny little holes, all the way up to the large ``maria'' seen
< on the Moon. Impact craters are usually round.
< ~ ~\\
< \begin{flushleft}
< 
< 1. On which of the five objects are large meteorite impact craters obvious? 
<  ({\bf 1 point})
< 
< ~ ~ \\
< 
< ~ ~ \\
< 
< 2. Does Venus or the Earth show any signs of large, round maria (like
< those seen on the Moon or Mercury)?
<  {\bf (1 point)}
< 
< ~ ~ \\
< 
< ~ ~ \\
< 
< 3. Which planet seems to have the most impact craters?
<  ({\bf 1 point})
< 
< ~ ~ \\
< 
< ~ ~\\
< 
< 4. Compare the surface of Mercury to the Moon. Are they similar?
<  {(\bf 3 points})
< 
< ~ ~\\
< \vspace{2.0in}
< 
< \end{flushleft}
< Mercury is the planet closest to the Sun, so it is the terrestrial planet
< that gets hit by comets, asteroids and meteoroids more often than the other 
< planets because the Sun's gravity tends to collect small bodies like comets 
< and asteroids. The closer you are to the Sun, the more of these objects 
< there are in the neighborhood. Over time, most of the largest asteroids on 
< orbits that intersect those of the other planets have either collided with a 
< planet, or have been broken into smaller pieces by the gravity of a close
< approach to a large
< planet. Thus, only smaller debris is left over to cause impact 
< craters.
< ~ ~\\
< 
< \begin{flushleft}
< 
< 5. Using the above information, make an educated guess on why Mercury does
< not have as many large maria as the Moon, even though both objects have been
< around for the same amount of time. [Hint: Maria are caused by the impacts
< of {\it large} bodies.]
<  ({\bf 3 points})
< 
< \vspace{3.0in}
< 
< \end{flushleft}
< Mercury and the Moon do not have atmospheres, while Mars has a thin atmosphere.
< Venus has the densest atmosphere of the terrestrial planets.
< ~ ~\\
< \begin{flushleft}
< 
< 6. Does the presence of an atmosphere appear to reduce the number of impact
< craters? Justify your answer.
<  ({\bf 3 points})
< 
< \vspace{2.0in}
< ~ ~\\
< 
< 
< {\bf Exercise \#2:} Global topography of Mercury, Venus, Earth, and Mars.
< At station \#2 you will find topographic maps of Mercury, Venus, the Earth, 
< and Mars. The data for Mercury has not been fully published, so we only have
< topographic maps for about 25\% of its surface. These maps are color-coded to 
< help you determine the highest and lowest parts
< of each planet. You can determine the elevation of a color-coded feature
< on these maps by using the scale found on each map. [Note that for the Earth
< and Mars, the scales of these maps are in meters, for Mercury it is in
< km (= 1,000 meters), while for Venus it is in 
< planetary radius! But the scale for Venus is the same as for Mars, so you
< can use the scale on the Mars map to examine Venus.]
< \end{flushleft}
< 
< \begin{flushleft}
< 7. Which planet seems to have the least amount of relief (relief =
< high and low features)?
<  ({\bf 2 points})
< 
< \vspace{0.8in}
< 
< 8. Which planet seems to have the deepest/lowest regions?
<  ({\bf 2 points})
< 
< \vspace{0.8in}
< 
< 9. Which planet seems to have the highest mountains?
<  ({\bf 2 points})
< 
< \vspace{0.8in}
< 
< On both the Venus and Mars topographic maps, the polar regions are plotted
< as separate circular maps so as to reduce distortion. 
< 
< ~ ~\\
< \clearpage
< 10. Looking at these polar plots, Mars appears to be a very strange planet.
< Compare the elevations of the northern and southern hemispheres of Mars.
< If Mars had an abundance of surface water (oceans), what would the planet look 
< like?  ({\bf 3 points})
< 
< \vspace{3.0in}
< 
< \end{flushleft}
< 
< \subsection{Detailed Comparison of the Surfaces of the Terrestrial Planets}
< 
< In this section we will compare some of the smaller surface features of
< the terrestrial planets using a variety of close-up images. In the following,
< the images of features on Venus have been made using
< radar (because the atmosphere of Venus is so cloudy, we cannot see its surface).
< While these images look similar to the pictures for the other planets,
< they differ in one major way: in radar, smooth objects reflect the radio
< waves differently than rough objects. In the radar images of Venus, the
< rough areas are ``brighter'' (whiter) than smooth areas.\\
< 
< In the Moon lab, there is a discussion on how impact craters form (in case
< you have not done that lab, read that discussion). For large impacts,
< the center of the crater may ``rebound'' and produce a central mountain (or
< several small peaks).
< Sometimes an impact is large enough to crack the surface of the planet,
< and lava flows into the crater filling it up, and making the floor of the
< crater smooth. On the Earth, water can also collect in a crater, while on
< Mars it might collect large quantities of dust. \\
< 
< \begin{flushleft}
< {\bf Exercise \#3:} Impact craters on the terrestrial planets. At station
< \#3 you will find close-up pictures of the surfaces of the terrestrial
< planets showing impact craters. 
< 
< ~ ~\\
< 
< 11. Compare the impact craters seen on Mercury, Venus, Earth, and Mars.
< How are they alike, how are they different? Are central mountain peaks
< common to craters on all planets? Of the sets of craters shown, does one
< planet seem to have more lava-filled craters than the others? ({\bf 4 points})
< 
< \clearpage
< ~ ~\\
< \vspace{2.0in}
< 
< 12. Which planet has the sharpest, roughest, most detailed and complex craters?
< [Hint: details include ripples in the nearby surface caused by the crater
< formation, as well as numerous small craters caused by large boulders thrown
< out of the bigger crater. Also commonly seen are ``ejecta blankets'' caused
< by material thrown out of the crater that settles near its outer edges.]
<  ({\bf 2 points})
< \vspace{1.0in}
< 
< 13. Which planet has the smoothest, and least detailed craters?
<  ({\bf 2 points})
< 
< \vspace{0.6in}
< 
< 14. What is the main difference between the planet you identified in question
< \#12 and that in question \#13? [Hint: what processes help erode craters?]
<  ({\bf 2 points})
< 
< \vspace{1.5in}
< \end{flushleft}
< 
< You have just examined four different craters found on the Earth: Berringer,
< Wolfe Creek, Mistastin Lake, and Manicouagan. Because we can visit these
< craters we can accurately determine when they were formed. Berringer is
< the youngest crater with an age of 49,000 years. Wolf Creek is the second
< youngest at 300,000 years. Mistastin Lake formed 38 million years ago, while
< Manicouagan is the oldest, easily identified crater on the surface of the
< Earth at 200 million years old.\\
< 
< \clearpage
< 15. Describe the differences between young and old craters on the Earth. What
< happens to these craters over time?  ({\bf 4 points})
< 
< \vspace{2.0in}
< 
< \subsection{Erosion Processes and Evidence for Water}
< 
< Geological erosion is the process of the breaking down, or the wearing-away
< of surface features due to a variety of processes.  Here we will be concerned
< with the two main erosion processes due to the presence of an atmosphere:
< wind erosion, and water erosion. With daytime temperatures above 700$^{\rm o}$F,
< both Mercury and Venus are too hot to have liquid water on their surfaces.
< In addition, Mercury has no atmosphere to sustain {\it water or a wind}. Interestingly,
< Venus has a very dense atmosphere, but as far as we can tell, very little
< wind erosion occurs at the surface. This is probably due to the incredible
< pressure at the surface of Venus due to its dense atmosphere: the atmospheric
< pressure at the surface of Venus is 90 times that at the surface of the
< Earth--it is like being 1 km below the surface of an Earth ocean! Thus,
< it is probably hard for strong winds to blow near the surface, and there
< are probably only gentle winds found there, and these do not seriously
< erode surface features. This is not true for the Earth or Mars.\\
< 
< On the surface of the Earth it is easy to see the effects of erosion by wind.
< For residents of New Mexico, we often have dust storms in the spring. During
< these events, dust is carried by the wind, and it can erode (``sandblast'')
< any surface it encounters, including rocks, boulders and mountains. Dust can
< also collect in cracks, arroyos, valleys, craters, or other low, protected
< regions. In some places, such as at the White Sands National Monument, large
< fields of sand dunes are created by wind-blown dust and sand.
< On the Earth, most large dune fields are located in arid regions. \\
< 
< \begin{flushleft}
< {\bf Exercise \#4:} Evidence for wind blown sand and dust on Earth and Mars.
< At station \#4 you will find some pictures of the Earth and Mars highlighting
< dune fields.
< 
< 
< \clearpage
< 16. Do the sand dunes of Earth and Mars appear to be very different? Do you
< think you could tell them apart in black and white photos? Given that
< the atmosphere of Mars is only 1\% of the Earth's, what does the presence of 
< sand dunes tell you about the winds on Mars?  ({\bf 3 points})
< 
< \vspace{1.5in}
< 
< \end{flushleft}
< 
< \begin{flushleft}
< {\bf Exercise \#5:} Looking for evidence of water on Mars. In this exercise,
< we will closely examine geological features on Earth caused by the erosion
< action of water. We will then compare these to similar features found
< on Mars. The photos are found at Station \#5.
< 
< ~ ~ \\
< 
< As you know, water tries to flow ``down hill'', constantly seeking the lowest
< elevation. On Earth most rivers eventually flow into one of the oceans. In
< arid regions, however, sometimes the river dries up before reaching the ocean,
< or it ends in a shallow lake that has no outlet to the sea. In the process
< of flowing down hill, water carves channels that have fairly unique shapes.
< A large river usually has an extensive, and complex drainage pattern.
< 
< ~ ~\\
< 
< 17. The drainage pattern for streams and rivers on Earth has been termed
< ``dendritic'', which means ``tree-like''. In the first photo at this station
< (\#23) is a dendritic drainage pattern for a region in Yemen. Why was the term
< dendritic used to describe such drainage patterns? Describe how this pattern
< is formed. ({\bf 3 points})
< 
< \vspace{1.5in}
< 
< 18. The next photo (\#24) is a picture of a sediment-rich river (note the brown
< water) entering a rather broad and flat region where it becomes shallow
< and spreads out. Describe the shapes of the ``islands'' formed by this
< river. ({\bf 3 points})
< \end{flushleft}
< \clearpage
< 
< In the next photo (\#25) is a picture of the northern part of the Nile river
< as it passes through Egypt. The Nile is 4,184 miles from its source to
< its mouth on the Mediterranean sea. It is formed in the highlands of Uganda
< and flows North, down hill to the Mediterranean. Most of Egypt is a very
< dry country, and there are no major rivers that flow into the Nile, thus
< there is no dendritic-like pattern to the Nile in Egypt. [Note that in this
< image of the Nile, there are several obvious dams that have created lakes
< and reservoirs.]
< ~ ~\\
< \begin{flushleft}
< 19. Describe what you see in this image from Mars (Photo \#26). ({\bf 2 points})
< 
< \vspace{1.0in}
< 
< 20. What is going on in this photo (\#27)? How were these features formed? Why do
< the small craters not show the same sort of ``teardrop'' shapes? ({\bf 2 points})
< 
< \vspace{1.0in}
< 
< 21. Here are some additional images of features on Mars. The second one 
< (Photo \#29) is a close-up of the region delineated by the white box seen in 
< Photo \#28. 
< Compare these to the Nile. ({\bf 2 points})
< 
< \vspace{1.0in}
< 
< 22. While Mars is dry now, what do you conclude about its past? Justify
< your answer. What technique can we use to determine when water might have 
< flowed in Mars' past? [Hint: see your answer for \#20.] ({\bf 4 points})
< 
< \end{flushleft}
< \clearpage
< 
< \subsection{Volcanoes and Tectonic Activity}
< 
< While water and wind-driven erosion is important in shaping the surface of
< a planet, there are other important events that can act to change the 
< appearance of a planet's surface: volcanoes, earthquakes, and plate tectonics.
< The majority of the volcanic and earthquake activity on Earth occurs near the 
< boundaries of large slabs of rock called ``plates''. As shown in Figure 
< \ref{figcutaway},
< the center of the Earth is very hot, and this heat flows from
< hot to cold, or from the center of the Earth to its surface (and into space).
< This heat transfer sets up a boiling motion in the semi-molten mantle
< of the Earth. \\
< 
< As shown in the next figure (Fig. \ref{figmantle}), in places where the heat rises,
< we get an up-welling of material that creates a ridge that forces the plates
< apart. We also get volcanoes at these boundaries. In other places, the crust
< of the Earth is pulled down into the mantle in what is called a subduction
< zone. Volcanoes and earthquakes are also common along subduction zone
< boundaries. There are other sources of earthquakes and volcanoes which are
< not directly associated with plate tectonic activity. For example,
< the Hawaiian islands are all volcanoes that have erupted in the middle of the
< Pacific plate. The crust of the Pacific plate is thin enough, and there is 
< sufficiently hot material below, to have caused the volcanic activity which
< created the chain of islands called Hawaii. In the next exercise
< we will examine the other terrestrial planets for evidence of volcanic
< and plate tectonic activity.\\
< 
< \begin{figure}[ht]
< \centerline{{\includegraphics[width=6.5cm]{Terrestrial/earth-layers.jpg}}}
< \caption{A cut away diagram of the structure of the Earth showing the hot
< core, the mantle, and the crust. The core of the Earth is very hot, and is
< composed of both liquid and solid iron. The mantle is a zone where the rocks
< are partially melted (``plastic-like''). The crust is the cold, outer skin
< of the Earth, and is very thin.}
< \label{figcutaway}
< \end{figure}
< 
< \begin{figure}[ht]
< \centerline{{\includegraphics[width=6cm]{Terrestrial/mantle.jpg}}}
< \caption{The escape of the heat from the Earth's core sets-up a boiling motion
< in the mantle. Where material rises to the surface it pushes apart the
< plates and volcanoes, and mountain chains are common. Where the material is 
< cooling, it flows downwards (subsides) back into the mantle pulling down on 
< the plates (``slab-pull'). This is how the large crustal plates move around on 
< the Earth's surface. }
< \label{figmantle}
< \end{figure}
< 
< {\bf Exercise \#6:} Using the topographical maps from station \#2, we
< will see if you can identify evidence for plate tectonics on the Earth.
< Note that plates have fairly distinct boundaries, usually long chains of
< mountains are present where two plates either are separating (forming long
< chains of volcanoes), or where two plates run into each other creating
< mountain ranges. Sometimes plates fracture, creating fairly straight lines
< (sometimes several parallel features are created). The remaining photos
< can be found at Station \#6.
< 
< \vspace{1.5in}
< \begin{flushleft}
< 23. Identify and describe several apparent tectonic features on the 
< topographic map of the Earth.
< [Hint: North and South America are moving away from Europe and Africa].
<  ({\bf 2 points})
< 
< \vspace{1.0in}
< 
< 24. Now, examine the topographic maps for Mars and Venus (ignoring the
< grey areas that are due to a lack of spacecraft data). Do you see any evidence
< for large scale tectonic activity on either Mars or Venus? ({\bf 3 points})
< 
< \vspace{1.8in}
< 
< \end{flushleft}
< 
< The fact that there is little large-scale tectonic activity present on the
< surfaces of either Mars or Venus today does not mean that they 
< never had any geological activity. Let us examine the volcanoes found
< on Venus, Earth and Mars. The first set of images contain views of a number of
< volcanoes on Earth. Several of these were produced using space-based radar
< systems carried aboard the Space Shuttle. In this way, they  better
< match the data for Venus. There are a variety of types of volcanoes on
< Earth, but there are two main classes of large volcanoes: ``shield'' and 
< ``composite''.
< Shield volcanoes are large, and have very gentle slopes. They are caused
< by low-viscosity lava that flows easily. They usually are rather flat on top,
< and often have a large ``caldera''
< (summit crater).  Composite volcanoes are more explosive,
< smaller, and have steeper sides (and ``pointier'' tops). Mount St. Helens is 
< one example of a composite volcano, and is the first picture (Photo \#31)
< at this station
< (note that the apparent crater at the top of St. Helens is due to the
< 1980 eruption that caused the North side of the volcano to collapse, and
< the field of devastation that emanates from there).
< The next two pictures are also of composite volcanoes while the last
< three are of the shield volcanoes Hawaii, Isabela and Miakijima (the last
< two in 3D).\\
< 
< ~ ~\
< \begin{flushleft}
< 25. Here are some images of Martian volcanoes (Photos \#37 to \#41). What one type of volcano
< does Mars have? How did you arrive at this answer? ({\bf 2 points})
< 
< \vspace{1.0in}
< 
< 
< 26. In the next set (Photos \#42 to \#44) are some false-color images of Venusian volcanoes.
< Among these are both overhead shots, and 3D images. Because Venus was
< mapped using radar, we can reconstruct the data to create images as
< if we were located on, or near, the surface of Venus. {\it Note, however, that
< the vertical elevation detail has been exaggerated by a factor of ten!}
< It might be hard to tell, but Venus is also dominated by one main type
< of Volcano, what is it? ({\bf 5 points})
< 
< \vspace{1.8in}
< \end{flushleft}
< %\clearpage
< %~ ~ ~\\
< \newpage
< \hspace*{3.0in}Name:{\hrulefill} \\
< \hspace*{3.25in}Date:{\hrulefill}\\
< 
< \subsection{Take Home Exercise (35 points total)}
< 
< As we have seen, many of the geological features common to the Earth can
< be found on the other terrestrial planets. Each planet, however, has its
< own peculiar geology. For example, Venus has the greatest number of volcanoes
< of any of the terrestrial planets, while Mars has the biggest volcanoes.
< Only the Earth seems to have active plate tectonics. Mercury appears to
< have had the least amount of geological activity in the solar system and,
< in this way, is quite similar to the Moon. Mars and the Earth share something
< that none of the other planets in our solar system do: erosion features
< due to liquid water. This, of course, is why there continues to be interest
< in searching for life (either alive or extinct) on Mars. On a separate
< sheet of paper, write a report answering the following questions:\\
< 
< \begin{itemize}
< \item Describe the surfaces of each of the terrestrial planets, and 
< the most important geological forces that have shaped their surfaces.
< 
< \item Of the four terrestrial planets, which one seems to be the least
< interesting? Can you think of one or more reasons why this planet is 
< so inactive?
< 
< \item If you were in charge of searching for life on Mars, where would you
< want to begin your search?
< 
< \end{itemize}
< 
< \subsection{Possible Quiz Questions}
< 
< \begin{flushleft}
< 
< 1. What are the main differences between Terrestrial and Jovian planets?\\
< 
< 2. What is density?\\
< 
< 3. How are impact craters formed?\\
< 
< 4. What is a topographic map?
< \end{flushleft}
< 
< \subsection{Extra Credit (ask your TA for permission before attempting, 5
< points)}
< 
< Since Mars currently has no large bodies of water, what is probably the most 
< important erosion process there? How can we tell? What is the best
< way to observe or monitor this type of erosion? Researching the images
< from the several small landers and some of the orbiting missions, is
< there strong evidence for this type of erosion? What is that evidence?\\
< %\clearpage
< %~ ~ ~\\
---
> \setcounter{figure}{0}
> \setcounter{table}{0}
> \setcounter{equation}{0}
> \hspace*{3.0in}Name:{\hrulefill} \\
> \hspace*{3.25in}Date:{\hrulefill}
> 
> \begin{Large}
> \section{\bf Introduction to the Geology of the Terrestrial Planets}
> \end{Large}
> 
> \subsection{Introduction}
> 
> There are two main families of planets in our solar system: the Terrestrial
> planets (Earth, Mercury, Venus, and Mars), and the Jovian Planets (Jupiter,
> Saturn, Uranus, and Neptune). The terrestrial planets are rocky planets
> that have properties similar to that of the Earth. While the Jovian planets
> are giant balls of gas. Table \ref{table:pproperties} summarizes the main properties of the
> planets in our solar system (Pluto is an oddball planet that does not fall into either
> categories, sharing many properties with the ``Kuiper belt'' objects discussed
> in the ``Comet Lab'').\\
>  
> \begin{table}[ht]
> \caption{The Properties of the Planets}
> \begin{center}
> \begin{tabular}{|c|c|c|c|}\hline
> Planet & Mass & Radius & Density\\
> ~ ~ ~  & (Earth Masses) & (Earth Radii) & gm/cm$^{\rm 3}$\\
> \hline
> Mercury& 0.055 & 0.38 & 5.5\\
> \hline
> Venus & 0.815 & 0.95 & 5.2 \\
> \hline
> Earth & 1.000 & 1.00 & 5.5\\
> \hline
> Mars  & 0.107 & 0.53 & 3.9\\
> \hline
> Jupiter& 318 & 10.8 & 1.4\\
> \hline
> Saturn & 95  & 9.0 & 0.7\\
> \hline
> Uranus & 14.5 & 3.93 & 1.3\\
> \hline
> Neptune & 17.2& 3.87 & 1.6\\
> \hline
> Pluto & 0.002 & 0.178 & 2.1 \\
> \hline
> \end{tabular}
> \end{center}
> \label{table:pproperties}
> \end{table}
> 
> It is clear from Table \ref{table:pproperties} that the nine planets in our solar system span
> a considerable range in sizes and masses. For example, the Earth has 18
> times the mass of Mercury, while Jupiter has 318 times the mass of the
> Earth. But the separation of the planets into Terrestrial and Jovian is
> not based on their masses or physical sizes, it is based on their densities (the
> last column in the table). What is density? Density is simply the mass of an 
> object divided by its volume: M/V. In the metric system, the density of
> water is set to 1.00 gm/cm$^{\rm 3}$. Densities for some materials you are 
> familiar with can be found in Table \ref{table:densities}.\\
> 
> \begin{table}
> \caption{The Densities of Common Materials}
> \begin{center}
> \begin{tabular}{|c|c|c|c|}\hline
> Element or & Density & Element & Density\\
> Molecule  & gm/cm$^{\rm 3}$ &~ ~ & gm/cm$^{\rm 3}$\\
> \hline
> Water& 1.0 & Carbon & 2.3\\
> \hline
> Aluminum & 2.7 & Silicon & 2.3 \\
> \hline
> Iron & 7.9 & Lead & 11.3\\
> \hline
> Gold  & 19.3 & Uranium & 19.1\\
> \hline
> \end{tabular}
> \end{center}
> \label{table:densities}
> \end{table}
> 
> If we examine the first table we see that the terrestrial planets all
> have higher densities than the Jovian planets. Mercury, Venus and Earth
> have densities above 5 gm/cm$^{\rm 3}$, while Mars has a slightly lower
> density ($\sim$ 4 gm/cm$^{\rm 3}$). The Jovian planets have densities
> very close to that of water--in fact, the mean density of Saturn is lower
> than that of water! The density of a planet gives us clues about its
> composition. If we look at the table of densities for common materials, we see 
> that the mean densities of the terrestrial planets are about halfway between 
> those of silicon 
> and iron. Both of these elements are highly abundant throughout the Earth, and
> thus we can postulate that the terrestrial planets are mostly composed
> of iron, silicon, with additional elements like carbon, oxygen, aluminum 
> and magnesium. The Jovian planets, however, must be mostly composed of
> lighter elements, such as hydrogen and helium. In fact, the Jovian
> planets have similar densities to that of the Sun: 1.4 gm/cm$^{\rm 3}$.
> The Sun is 70\% hydrogen, and 28\% helium. Except for small, rocky cores, the
> Jovian planets are almost nothing but hydrogen and helium.\\
> 
> The terrestrial planets share other properties, for example they all rotate
> much more slowly than the Jovian planets. They also have much thinner
> atmospheres than the Jovian planets (which are almost {\it all} atmosphere!).
> Today we want to investigate the geologies of the terrestrial planets to
> see if we can find other similarities, or identify interesting differences.
> 
> \subsection{Topographic Map Projections}
> 
> In the first part of this lab we will take a look at images and maps of
> the surfaces of the terrestrial planets for comparison. But before we do so,
> we must talk about what you will be viewing, and how these maps/images
> were produced. As you probably know, 75\% of the Earth's surface is covered by 
> oceans, thus
> a picture of the Earth from space does not show very much of the actual
> rocky surface (the ``crust'' of the Earth). With modern techniques (sonar,
> radar, etc.) it is possible to reconstruct the true shape and structure
> of a planet's rocky surface, whether it is covered in water, or by very
> thick clouds (as is the case for Venus). Such maps of the ``relief'' of the 
> surface of a planet are called {\it topographic} maps. These maps usually color
> code, or have contours, showing the highs and lows of the surface elevations.
> Regions of constant elevation above (or below) sea level all will have the
> same color. This way, large structures such as mountain ranges, or ocean 
> basins, stand out very clearly.\\
> 
> There are several ways to present topographic maps, and you will see two
> versions today. One type of map is an attempt at a 3D
> {\it visualization} that keeps the relative sizes of the continents in
> correct proportion (see Figure \ref{figsphthreeD}, below). But such maps only allow you to see a small
> part of a spherical planet in any one plot. More commonly, the entire
> surface of the planet is presented as a rectangular map as shown in
> Figure \ref{figtopo}. Because the
> surface of a sphere cannot be properly represented as a rectangle, the
> regions near the north and south poles of a planet end up being highly 
> distorted in this kind of map. So keep this in mind as you work through
> the exercises in this lab.
> 
> \begin{figure}[ht]
> \centerline{{\includegraphics[width=5cm]{Terrestrial/usearth.jpg}}}
> \caption{A topographic map showing one hemisphere of Earth centered on North
> America. In this 3D representation the continents are correctly rendered.}
> \label{figsphthreeD}
> \end{figure}
> 
> \begin{figure}[ht]
> \centerline{{\includegraphics[width=6cm]{Terrestrial/globalrelief.jpg}}}
> \caption{A topographic map showing the entire surface of the Earth.
> In this 2D representation, the continents are incorrectly rendered. Note
> that Antarctica (the land mass that spans the bottom border of this map)
> is 50\% smaller than North America, but here appears massive. You might
> also be able to compare
> the size of Greenland on this map, to that of the previous map.}
> \label{figtopo}
> \end{figure}
> 
> \subsection{Global Comparisons}
> 
> In the first part of this lab exercise, you will look at the planets 
> in a {\it global} sense, by comparing the largest structures on the 
> terrestrial planets.  Note that Mercury has recently been visited by
> the Messenger spacecraft. Much new data has recently become available, but
> we do not yet have the same type of plots for Mercury as we do for the other
> planets.
> ~ ~\\
> \begin{flushleft}
> {\bf Exercise \#1}: At station \#1 you will find images of Mercury, Venus,
> the Earth, the Moon, and Mars. The images for Mercury, Venus and the Earth
> and Moon are in a ``false color'' to help emphasize different types of
> rocks or large-scale structures. The image of Mars, however, is in ``true 
> color''.
> \end{flushleft}
> ~ ~\\
> Impact craters can come in a variety of
> sizes, from tiny little holes, all the way up to the large ``maria'' seen
> on the Moon. Impact craters are usually round.
> ~ ~\\
> \begin{flushleft}
> 
> 1. On which of the five objects are large meteorite impact craters obvious? 
>  ({\bf 1 point})
> 
> ~ ~ \\
> 
> ~ ~ \\
> 
> 2. Does Venus or the Earth show any signs of large, round maria (like
> those seen on the Moon or Mercury)?
>  {\bf (1 point)}
> 
> ~ ~ \\
> 
> ~ ~ \\
> 
> 3. Which planet seems to have the most impact craters?
>  ({\bf 1 point})
> 
> ~ ~ \\
> 
> ~ ~\\
> 
> 4. Compare the surface of Mercury to the Moon. Are they similar?
>  {(\bf 3 points})
> 
> ~ ~\\
> \vspace{2.0in}
> 
> \end{flushleft}
> Mercury is the planet closest to the Sun, so it is the terrestrial planet
> that gets hit by comets, asteroids and meteoroids more often than the other 
> planets because the Sun's gravity tends to collect small bodies like comets 
> and asteroids. The closer you are to the Sun, the more of these objects 
> there are in the neighborhood. Over time, most of the largest asteroids on 
> orbits that intersect those of the other planets have either collided with a 
> planet, or have been broken into smaller pieces by the gravity of a close
> approach to a large
> planet. Thus, only smaller debris is left over to cause impact 
> craters.
> ~ ~\\
> 
> \begin{flushleft}
> 
> 5. Using the above information, make an educated guess on why Mercury does
> not have as many large maria as the Moon, even though both objects have been
> around for the same amount of time. [Hint: Maria are caused by the impacts
> of {\it large} bodies.]
>  ({\bf 3 points})
> 
> \vspace{3.0in}
> 
> \end{flushleft}
> Mercury and the Moon do not have atmospheres, while Mars has a thin atmosphere.
> Venus has the densest atmosphere of the terrestrial planets.
> ~ ~\\
> \begin{flushleft}
> 
> 6. Does the presence of an atmosphere appear to reduce the number of impact
> craters? Justify your answer.
>  ({\bf 3 points})
> 
> \vspace{2.0in}
> ~ ~\\
> 
> 
> {\bf Exercise \#2:} Global topography of Mercury, Venus, Earth, and Mars.
> At station \#2 you will find topographic maps of Mercury, Venus, the Earth, 
> and Mars. The data for Mercury has not been fully published, so we only have
> topographic maps for about 25\% of its surface. These maps are color-coded to 
> help you determine the highest and lowest parts
> of each planet. You can determine the elevation of a color-coded feature
> on these maps by using the scale found on each map. [Note that for the Earth
> and Mars, the scales of these maps are in meters, for Mercury it is in
> km (= 1,000 meters), while for Venus it is in 
> planetary radius! But the scale for Venus is the same as for Mars, so you
> can use the scale on the Mars map to examine Venus.]
> \end{flushleft}
> 
> \begin{flushleft}
> 7. Which planet seems to have the least amount of relief (relief =
> high and low features)?
>  ({\bf 2 points})
> 
> \vspace{0.8in}
> 
> 8. Which planet seems to have the deepest/lowest regions?
>  ({\bf 2 points})
> 
> \vspace{0.8in}
> 
> 9. Which planet seems to have the highest mountains?
>  ({\bf 2 points})
> 
> \vspace{0.8in}
> 
> On both the Venus and Mars topographic maps, the polar regions are plotted
> as separate circular maps so as to reduce distortion. 
> 
> ~ ~\\
> \clearpage
> 10. Looking at these polar plots, Mars appears to be a very strange planet.
> Compare the elevations of the northern and southern hemispheres of Mars.
> If Mars had an abundance of surface water (oceans), what would the planet look 
> like?  ({\bf 3 points})
> 
> \vspace{3.0in}
> 
> \end{flushleft}
> 
> \subsection{Detailed Comparison of the Surfaces of the Terrestrial Planets}
> 
> In this section we will compare some of the smaller surface features of
> the terrestrial planets using a variety of close-up images. In the following,
> the images of features on Venus have been made using
> radar (because the atmosphere of Venus is so cloudy, we cannot see its surface).
> While these images look similar to the pictures for the other planets,
> they differ in one major way: in radar, smooth objects reflect the radio
> waves differently than rough objects. In the radar images of Venus, the
> rough areas are ``brighter'' (whiter) than smooth areas.\\
> 
> In the Moon lab, there is a discussion on how impact craters form (in case
> you have not done that lab, read that discussion). For large impacts,
> the center of the crater may ``rebound'' and produce a central mountain (or
> several small peaks).
> Sometimes an impact is large enough to crack the surface of the planet,
> and lava flows into the crater filling it up, and making the floor of the
> crater smooth. On the Earth, water can also collect in a crater, while on
> Mars it might collect large quantities of dust. \\
> 
> \begin{flushleft}
> {\bf Exercise \#3:} Impact craters on the terrestrial planets. At station
> \#3 you will find close-up pictures of the surfaces of the terrestrial
> planets showing impact craters. 
> 
> ~ ~\\
> 
> 11. Compare the impact craters seen on Mercury, Venus, Earth, and Mars.
> How are they alike, how are they different? Are central mountain peaks
> common to craters on all planets? Of the sets of craters shown, does one
> planet seem to have more lava-filled craters than the others? ({\bf 4 points})
> 
> \clearpage
> ~ ~\\
> \vspace{2.0in}
> 
> 12. Which planet has the sharpest, roughest, most detailed and complex craters?
> [Hint: details include ripples in the nearby surface caused by the crater
> formation, as well as numerous small craters caused by large boulders thrown
> out of the bigger crater. Also commonly seen are ``ejecta blankets'' caused
> by material thrown out of the crater that settles near its outer edges.]
>  ({\bf 2 points})
> \vspace{1.0in}
> 
> 13. Which planet has the smoothest, and least detailed craters?
>  ({\bf 2 points})
> 
> \vspace{0.6in}
> 
> 14. What is the main difference between the planet you identified in question
> \#12 and that in question \#13? [Hint: what processes help erode craters?]
>  ({\bf 2 points})
> 
> \vspace{1.5in}
> \end{flushleft}
> 
> You have just examined four different craters found on the Earth: Berringer,
> Wolfe Creek, Mistastin Lake, and Manicouagan. Because we can visit these
> craters we can accurately determine when they were formed. Berringer is
> the youngest crater with an age of 49,000 years. Wolf Creek is the second
> youngest at 300,000 years. Mistastin Lake formed 38 million years ago, while
> Manicouagan is the oldest, easily identified crater on the surface of the
> Earth at 200 million years old.\\
> 
> \clearpage
> 15. Describe the differences between young and old craters on the Earth. What
> happens to these craters over time?  ({\bf 4 points})
> 
> \vspace{2.0in}
> 
> \subsection{Erosion Processes and Evidence for Water}
> 
> Geological erosion is the process of the breaking down, or the wearing-away
> of surface features due to a variety of processes.  Here we will be concerned
> with the two main erosion processes due to the presence of an atmosphere:
> wind erosion, and water erosion. With daytime temperatures above 700$^{\rm o}$F,
> both Mercury and Venus are too hot to have liquid water on their surfaces.
> In addition, Mercury has no atmosphere to sustain {\it water or a wind}. Interestingly,
> Venus has a very dense atmosphere, but as far as we can tell, very little
> wind erosion occurs at the surface. This is probably due to the incredible
> pressure at the surface of Venus due to its dense atmosphere: the atmospheric
> pressure at the surface of Venus is 90 times that at the surface of the
> Earth--it is like being 1 km below the surface of an Earth ocean! Thus,
> it is probably hard for strong winds to blow near the surface, and there
> are probably only gentle winds found there, and these do not seriously
> erode surface features. This is not true for the Earth or Mars.\\
> 
> On the surface of the Earth it is easy to see the effects of erosion by wind.
> For residents of New Mexico, we often have dust storms in the spring. During
> these events, dust is carried by the wind, and it can erode (``sandblast'')
> any surface it encounters, including rocks, boulders and mountains. Dust can
> also collect in cracks, arroyos, valleys, craters, or other low, protected
> regions. In some places, such as at the White Sands National Monument, large
> fields of sand dunes are created by wind-blown dust and sand.
> On the Earth, most large dune fields are located in arid regions. \\
> 
> \begin{flushleft}
> {\bf Exercise \#4:} Evidence for wind blown sand and dust on Earth and Mars.
> At station \#4 you will find some pictures of the Earth and Mars highlighting
> dune fields.
> 
> 
> \clearpage
> 16. Do the sand dunes of Earth and Mars appear to be very different? Do you
> think you could tell them apart in black and white photos? Given that
> the atmosphere of Mars is only 1\% of the Earth's, what does the presence of 
> sand dunes tell you about the winds on Mars?  ({\bf 3 points})
> 
> \vspace{1.5in}
> 
> \end{flushleft}
> 
> \begin{flushleft}
> {\bf Exercise \#5:} Looking for evidence of water on Mars. In this exercise,
> we will closely examine geological features on Earth caused by the erosion
> action of water. We will then compare these to similar features found
> on Mars. The photos are found at Station \#5.
> 
> ~ ~ \\
> 
> As you know, water tries to flow ``down hill'', constantly seeking the lowest
> elevation. On Earth most rivers eventually flow into one of the oceans. In
> arid regions, however, sometimes the river dries up before reaching the ocean,
> or it ends in a shallow lake that has no outlet to the sea. In the process
> of flowing down hill, water carves channels that have fairly unique shapes.
> A large river usually has an extensive, and complex drainage pattern.
> 
> ~ ~\\
> 
> 17. The drainage pattern for streams and rivers on Earth has been termed
> ``dendritic'', which means ``tree-like''. In the first photo at this station
> (\#23) is a dendritic drainage pattern for a region in Yemen. Why was the term
> dendritic used to describe such drainage patterns? Describe how this pattern
> is formed. ({\bf 3 points})
> 
> \vspace{1.5in}
> 
> 18. The next photo (\#24) is a picture of a sediment-rich river (note the brown
> water) entering a rather broad and flat region where it becomes shallow
> and spreads out. Describe the shapes of the ``islands'' formed by this
> river. ({\bf 3 points})
> \end{flushleft}
> \clearpage
> 
> In the next photo (\#25) is a picture of the northern part of the Nile river
> as it passes through Egypt. The Nile is 4,184 miles from its source to
> its mouth on the Mediterranean sea. It is formed in the highlands of Uganda
> and flows North, down hill to the Mediterranean. Most of Egypt is a very
> dry country, and there are no major rivers that flow into the Nile, thus
> there is no dendritic-like pattern to the Nile in Egypt. [Note that in this
> image of the Nile, there are several obvious dams that have created lakes
> and reservoirs.]
> ~ ~\\
> \begin{flushleft}
> 19. Describe what you see in this image from Mars (Photo \#26). ({\bf 2 points})
> 
> \vspace{1.0in}
> 
> 20. What is going on in this photo (\#27)? How were these features formed? Why do
> the small craters not show the same sort of ``teardrop'' shapes? ({\bf 2 points})
> 
> \vspace{1.0in}
> 
> 21. Here are some additional images of features on Mars. The second one 
> (Photo \#29) is a close-up of the region delineated by the white box seen in 
> Photo \#28. 
> Compare these to the Nile. ({\bf 2 points})
> 
> \vspace{1.0in}
> 
> 22. While Mars is dry now, what do you conclude about its past? Justify
> your answer. What technique can we use to determine when water might have 
> flowed in Mars' past? [Hint: see your answer for \#20.] ({\bf 4 points})
> 
> \end{flushleft}
> \clearpage
> 
> \subsection{Volcanoes and Tectonic Activity}
> 
> While water and wind-driven erosion is important in shaping the surface of
> a planet, there are other important events that can act to change the 
> appearance of a planet's surface: volcanoes, earthquakes, and plate tectonics.
> The majority of the volcanic and earthquake activity on Earth occurs near the 
> boundaries of large slabs of rock called ``plates''. As shown in Figure 
> \ref{figcutaway},
> the center of the Earth is very hot, and this heat flows from
> hot to cold, or from the center of the Earth to its surface (and into space).
> This heat transfer sets up a boiling motion in the semi-molten mantle
> of the Earth. \\
> 
> As shown in the next figure (Fig. \ref{figmantle}), in places where the heat rises,
> we get an up-welling of material that creates a ridge that forces the plates
> apart. We also get volcanoes at these boundaries. In other places, the crust
> of the Earth is pulled down into the mantle in what is called a subduction
> zone. Volcanoes and earthquakes are also common along subduction zone
> boundaries. There are other sources of earthquakes and volcanoes which are
> not directly associated with plate tectonic activity. For example,
> the Hawaiian islands are all volcanoes that have erupted in the middle of the
> Pacific plate. The crust of the Pacific plate is thin enough, and there is 
> sufficiently hot material below, to have caused the volcanic activity which
> created the chain of islands called Hawaii. In the next exercise
> we will examine the other terrestrial planets for evidence of volcanic
> and plate tectonic activity.\\
> 
> \begin{figure}[ht]
> \centerline{{\includegraphics[width=6.5cm]{Terrestrial/earth-layers.jpg}}}
> \caption{A cut away diagram of the structure of the Earth showing the hot
> core, the mantle, and the crust. The core of the Earth is very hot, and is
> composed of both liquid and solid iron. The mantle is a zone where the rocks
> are partially melted (``plastic-like''). The crust is the cold, outer skin
> of the Earth, and is very thin.}
> \label{figcutaway}
> \end{figure}
> 
> \begin{figure}[ht]
> \centerline{{\includegraphics[width=6cm]{Terrestrial/mantle.jpg}}}
> \caption{The escape of the heat from the Earth's core sets-up a boiling motion
> in the mantle. Where material rises to the surface it pushes apart the
> plates and volcanoes, and mountain chains are common. Where the material is 
> cooling, it flows downwards (subsides) back into the mantle pulling down on 
> the plates (``slab-pull'). This is how the large crustal plates move around on 
> the Earth's surface. }
> \label{figmantle}
> \end{figure}
> 
> {\bf Exercise \#6:} Using the topographical maps from station \#2, we
> will see if you can identify evidence for plate tectonics on the Earth.
> Note that plates have fairly distinct boundaries, usually long chains of
> mountains are present where two plates either are separating (forming long
> chains of volcanoes), or where two plates run into each other creating
> mountain ranges. Sometimes plates fracture, creating fairly straight lines
> (sometimes several parallel features are created). The remaining photos
> can be found at Station \#6.
> 
> \vspace{1.5in}
> \begin{flushleft}
> 23. Identify and describe several apparent tectonic features on the 
> topographic map of the Earth.
> [Hint: North and South America are moving away from Europe and Africa].
>  ({\bf 2 points})
> 
> \vspace{1.0in}
> 
> 24. Now, examine the topographic maps for Mars and Venus (ignoring the
> grey areas that are due to a lack of spacecraft data). Do you see any evidence
> for large scale tectonic activity on either Mars or Venus? ({\bf 3 points})
> 
> \vspace{1.8in}
> 
> \end{flushleft}
> 
> The fact that there is little large-scale tectonic activity present on the
> surfaces of either Mars or Venus today does not mean that they 
> never had any geological activity. Let us examine the volcanoes found
> on Venus, Earth and Mars. The first set of images contain views of a number of
> volcanoes on Earth. Several of these were produced using space-based radar
> systems carried aboard the Space Shuttle. In this way, they  better
> match the data for Venus. There are a variety of types of volcanoes on
> Earth, but there are two main classes of large volcanoes: ``shield'' and 
> ``composite''.
> Shield volcanoes are large, and have very gentle slopes. They are caused
> by low-viscosity lava that flows easily. They usually are rather flat on top,
> and often have a large ``caldera''
> (summit crater).  Composite volcanoes are more explosive,
> smaller, and have steeper sides (and ``pointier'' tops). Mount St. Helens is 
> one example of a composite volcano, and is the first picture (Photo \#31)
> at this station
> (note that the apparent crater at the top of St. Helens is due to the
> 1980 eruption that caused the North side of the volcano to collapse, and
> the field of devastation that emanates from there).
> The next two pictures are also of composite volcanoes while the last
> three are of the shield volcanoes Hawaii, Isabela and Miakijima (the last
> two in 3D).\\
> 
> ~ ~\
> \begin{flushleft}
> 25. Here are some images of Martian volcanoes (Photos \#37 to \#41). What one type of volcano
> does Mars have? How did you arrive at this answer? ({\bf 2 points})
> 
> \vspace{1.0in}
> 
> 
> 26. In the next set (Photos \#42 to \#44) are some false-color images of Venusian volcanoes.
> Among these are both overhead shots, and 3D images. Because Venus was
> mapped using radar, we can reconstruct the data to create images as
> if we were located on, or near, the surface of Venus. {\it Note, however, that
> the vertical elevation detail has been exaggerated by a factor of ten!}
> It might be hard to tell, but Venus is also dominated by one main type
> of Volcano, what is it? ({\bf 5 points})
> 
> \vspace{1.8in}
> \end{flushleft}
> \clearpage
> ~ ~ ~\\
> \newpage
> \hspace*{3.0in}Name:{\hrulefill} \\
> \hspace*{3.25in}Date:{\hrulefill}\\
> 
> \subsection{Take Home Exercise (35 points total)}
> 
> As we have seen, many of the geological features common to the Earth can
> be found on the other terrestrial planets. Each planet, however, has its
> own peculiar geology. For example, Venus has the greatest number of volcanoes
> of any of the terrestrial planets, while Mars has the biggest volcanoes.
> Only the Earth seems to have active plate tectonics. Mercury appears to
> have had the least amount of geological activity in the solar system and,
> in this way, is quite similar to the Moon. Mars and the Earth share something
> that none of the other planets in our solar system do: erosion features
> due to liquid water. This, of course, is why there continues to be interest
> in searching for life (either alive or extinct) on Mars. On a separate
> sheet of paper, write a report answering the following questions:\\
> 
> \begin{itemize}
> \item Describe the surfaces of each of the terrestrial planets, and 
> the most important geological forces that have shaped their surfaces.
> 
> \item Of the four terrestrial planets, which one seems to be the least
> interesting? Can you think of one or more reasons why this planet is 
> so inactive?
> 
> \item If you were in charge of searching for life on Mars, where would you
> want to begin your search?
> 
> \end{itemize}
> 
> \subsection{Possible Quiz Questions}
> 
> \begin{flushleft}
> 
> 1. What are the main differences between Terrestrial and Jovian planets?\\
> 
> 2. What is density?\\
> 
> 3. How are impact craters formed?\\
> 
> 4. What is a topographic map?
> \end{flushleft}
> 
> \subsection{Extra Credit (ask your TA for permission before attempting, 5
> points)}
> 
> Since Mars currently has no large bodies of water, what is probably the most 
> important erosion process there? How can we tell? What is the best
> way to observe or monitor this type of erosion? Researching the images
> from the several small landers and some of the orbiting missions, is
> there strong evidence for this type of erosion? What is that evidence?\\
> \clearpage
> ~ ~ ~\\