AstronomyAdditional Resources.docxFor this weeks website, .docx

Astronomy/Additional Resources.docx
For this week's website, how about some very pretty pictures of
the Earth from space? The Landsat series of satellites have been
imaging the Earth since 1972, and you can look at a lot of these
images at eros.usgs.gov/imagegallery/. On February 11, 2013,
Landsat 5 received the title "Longest-operating Earth
observation satellite" according to the Guinness Book of World
Records, outliving its three-year design life by a quarter of a
century, for its 28 years 10 months (and counting) time on orbit.
That same day, the newest Landsat satellite (LDCM, Landsat
Data Continuity Mission) was launched. After three months of
testing, it officially became known as Landsat 8 on May 30,
2013.
Also, take a look at this site about the Mars Exploration Rovers:
marsrovers.jpl.nasa.gov/home/index.html. The rover Spirit has
been declared dead after traveling 4.8 miles. Opportunity, on
the other hand, is still going strong, having traveled over 26
miles. This is pretty amazing for two rovers that were designed
to last for three months (it's been almost 13 years since they
landed). Talk about going past warranty!
The Mars Science Laboratory rover Curiosity launched on
November 26, 2011 and landed on Mars on August 6, 2012.
Follow it at the mission website: mars.jpl.nasa.gov/msl/ or its
Facebook page at www.facebook.com/MarsCuriosity.
Astronomy/Assignment Instructions.docx
Assignment Instructions
Instructions: All details for completing this lab are in the
weekly lesson. Download the provided Word document and

carefully follow all instructions both in the lesson and in the
Word document. You will enter your work in a separate file,
following the file naming convention in the lesson description.
Submission: Upload your Word document, or you may also save
and upload your work as a PDF file. Any appropriate sketches,
diagrams, etc. may be pasted into the Word document or
uploaded as a separate image file.
Rubric: Your score will be based on the following rubric. As
you can see, phases V and VI constitute the majority of points
for the lab. If you are having difficulty, don't leave a section
blank...ask questions! You may post questions in the Lab Q&A
forum (in which case your classmates and/or the instructor can
respond, and the answer will benefit the whole class), or
directly in a message to the instructor.
Phase I - done/not done (if not done, 1 point will be subtracted)
Phase II - 1 point
Phase III - 1 point
Phase IV - 1 point
Phase V - Research question - 1 point
Phase V - Procedure - 1 point
Phase V - Data - 1 point
Phase V - Evidence-based conclusion - 1 point
Phase VI - Summary - 3 points
Astronomy/BEFORE YOU BEGIN .docx
BEFORE YOU BEGIN - This is important for all of the labs.
Create a new document for your responses with the following
naming convention:
Lastname_Firstname_Constellation_Lab.doc.
For example, Smith_John_Constellation_Lab.doc.

Type your responses into your blank document, being careful to
include headings for the six sections of the lab (Phase I through
Phase VI) and any question numbers. To submit your
assignment, upload this document plus any additional
documents you may have, such as screenshots of your data (or
you can paste those directly into your document). All submitted
labs will be automatically scanned by the anti-plagiarism
Turnitin.com.
Phase I—You're using www.heavens-above.com again for this
lab. Follow the instructions in questions 1 through 8, and enter
your answers directly in the Word document.
Phase II—You will now use the site to answer some questions
and then analyze a provided generalization based on your
evidence.
Phase III—You are given some data collected from the site, and
asked to come up with a conclusion based on that data (in other
words, an evidence-based conclusion). Make sure that you
mention the specific pieces of data that you are using for
evidence.
Phase IV—In this phase, you are given a research question and
asked to come up with a step-by-step method of collecting the
evidence needed to answer this question. You do not need to do
the whole data collection process, but you do need to explain
what someone would need to do (again, further instructions are
in the lab document). Use the Heavens-Above.com site, which
means you shouldn't write out a procedure for answering this
question using real-world observations. Write it so that someone
else could follow your step-by-step procedure to successfully
collect the needed data.
Phase V—Now, based on what you have done in the first four
phases, you will come up with your own answerable research

question that can be answered using the Heavens Above (or
similar) site. Don't worry, the question does not need to be
complex or sophisticated, but it does need to be answerable, by
you, using this website. You will write your question, the
procedure to collect the evidence (like in phase IV), collect the
data (use the data table in phase III as a rough guide), and come
to an evidence-based conclusion (like you did in phase III).
Phase VI—Finally, you will write a short (50-word) summary
(details in the lab document). This should not be information
from your textbook or other sources.
Lastly, upload your completed lab document to the assignments
area (remember that your name must be in the name of the file).
Questions—Post any questions about the lab to the Lab Q&A
Forum. Please include the lab number in your subject line. You
can also send me a message with questions.
Additional fun—You may have noticed something interesting in
Phase IV. I highly recommend watching this video:
casa.colorado.edu/~dduncan/pseudoscience/Derren_Brown_Astr
ology.avi.
Astronomy/Chapter5.ppt
Investigating Astronomy
Timothy F. Slater, Roger A. Freedman

Chapter 5
Uncovering Earth’s Systems
Welcome to week 5! This week, we are going to focus on our
home planet, Earth. This is the only planet that we can so far
examine in detail, and so learning about it can help us to learn
about other planets. While the other planets in our solar system
obviously aren't Earth-like, there are similarities.
*
Earth’s layered interior is revealed
by the study of earthquakes.The majority of Earth’s internal
energy comes from radioactive decay of elements deep inside
Earth (uranium, thorium, potassium, etc.).This energy drives
geologic activity that profoundly affects Earth’s surface.
Earth's interior consists of several layers, which we can learn
about by studying earthquakes. Earth has a significant amount
of energy, and most of that internal energy comes from the
radioactive decay of elements inside the planet (including
uranium, thorium, potassium, etc.). This is the energy that
powers geologic activity that changes the Earth's surface.
*
Three Types of Rocks1) Igneous rocks form when minerals cool
from a molten state. The ocean floor is made predominantly of
basalt.Magma: molten rock buried below the surface Lava:
molten rock flowing out upon the surface (e.g., volcanic

eruptions)
Before we go more “in-depth” into the Earth (pun intended),
let's first look at the surface. There are three types of rocks.
Igneous rock forms when minerals cool and harden from a
molten state. This picture here is of a type of igneous rock
called basalt, which is largely what the ocean floor is composed
of. When this rock is still molten (liquid) and is buried below
the surface, it is called magma. When the molten rock flows out
upon the surface of the planet, it is called lava. You can search
the Internet for very cool images and movies of lava flows,
especially in Hawaii. It is amazing to watch the Earth changing
in front of your eyes.
*
Three Types of Rocks2) Sedimentary rocks are by-products of
erosion―the action of wind, water, or ice that loosens rock or
soil and moves it downhill or downstream.Example: Sandstone
Winds pile up layer upon layer of sand grains.
Cementation: materials present amid the sand can gradually
cement the grains together.Example: Limestone
Minerals that precipitate out of the oceans cover the ocean
floor.
The second type of rock is called sedimentary. These are rocks
that are caused by the process of erosion, which is wind, water,
or ice moving rock and sand. Sandstone, which is pictured here,
is one example. It is created when layer upon layer of sand
grains are piled up by wind. The sand grains get glued together
in a process called cementation. Another example of
sedimentary rock is limestone, which is minerals that precipitate
out of ocean water onto the ocean floor, creating layers.

*
Three Types of Rocks3) Metamorphic rocks form where rocks
are exposed to enormous pressure and/or high
temperatures.Severe conditions change the structure of the
rocks.Earth’s geologic processes are dramatic enough to lift up
to the surface material from deep within the crust!
The third type of rock is known as metamorphic. These rocks
have been exposed to enormous pressure and/or high
temperature. The pressure and/or temperature actually changes
the structure of the rock (like the marble seen here, which is
caused by changes to sedimentary limestone, or the schist on the
right, which is formed from changes to igneous rock). These
changes must occur deep inside the Earth's crust, because that is
where the enormous pressure and temperature is. The presence
of metamorphic rocks on or near the surface is evidence that the
geologic processes on Earth are dramatic enough to bring
material to the surface from deep within the crust.
*
An Iron-Rich Planet
As we saw in Chapter 4, the density of an object is equal to its
mass (the amount of “stuff” in it) divided by its volume (the
space it takes up). The densities of typical rocks on the surface
of the Earth are about 3000 kg per cubic meter. However, the
average density of the whole Earth is 5515 kg per cubic meter.
Therefore, the interior of the Earth must be composed of denser
materials than those on the surface, in order to bring that

average up. So, why would the interior of the Earth be denser
than the surface? Soon after the Earth's formation, about 4.56
billion years ago, it was mostly molten. The energy to keep it
molten would have come from numerous impacts of objects
from space plus the radioactive decay of elements. Gravity
would have pulled more on denser material, like iron, causing it
to sink towards the center. This would have displaced less dense
material, causing that material to move toward the surface. This
process is known as differentiation, and eventually led to the
Earth having an iron core, surrounded by less dense rocky
material. The core is made up of two parts: a solid inner core
and a liquid outer core. This is due to the fact that the inner
core experiences more pressure, being at the very center of the
Earth. When a material is at a higher pressure, its melting point
is higher. So the inner core, while hotter than the outer core,
isn’t as hot as the melting point of iron at that pressure.
Surrounding the core is the mantle, which is composed of iron-
and silicon-rich rock (partially solid and partially liquid). The
outer layer is the solid crust. Incidentally, how do we know that
the dense material at the center of the Earth is iron? Well, iron
is a good candidate first because it is very massive, and second
because there is a lot of it. It is the seventh most abundant
element in our part of our galaxy. That means, that not only is it
dense enough to sink to the center during differentiation, but
that there would have been enough of it present in the early
solar system to give the Earth its core. The more abundant
elements (hydrogen, helium, oxygen, carbon, neon, and
nitrogen) are not massive enough to account for the density of
the Earth.
*
Seismic WavesEarthquakes produce different kinds of
waves.Surface waves are like ocean waves.P waves are
longitudinal waves, like pushing a spring in and out. S waves

are transverse waves, shaking a rope upand down.
In order to talk about how we use earthquakes to learn about the
interior of the Earth, we first need to discuss seismic waves.
Earthquakes produces different kinds of waves. First are the
surface waves, that are sort of like waves on the ocean. These
cause the rolling motion that people often feel during an
earthquake. The other kinds of waves travel through the interior
of the Earth. P waves are longitudinal, which means they
vibrate forward and back. You can think of these waves like
moving a spring or a slinky in and out. The P stands for
primary. S waves (for secondary) are transverse waves, which
means they vibrate up and down. You can think of these like a
rope being waved up and down.
*
Earthquake Waves as Earth ProbesSeismic waves follow curved
paths because of differences in the density and composition of
the material in the Earth’s interior. Paths curve gradually where
there are gradual changes in density and composition. Sharp
bends occur only where there is an abrupt change from one kind
of material to another―the boundary between the outer core and
the mantle. Only P waves can pass through the Earth’s liquid
outer core.
As the seismic waves move through the interior of the Earth,
their paths get curved because of the differences in density and
composition of the material. Where there are gradual changes,
their paths curve gradually. Where there are abrupt changes (for
example, at the boundary between the outer core and mantle),
there are sharp changes in the direction of the seismic waves.
Only the P waves can travel through the liquid outer core, so the

S waves cannot reach the opposite side of the planet from where
the earthquake occurs.
*
Earth’s Major LayersEvidence indicates a liquid outer core
sandwiched between a solid inner core and a mostly solid
mantle. Both temperature and pressure increase with increasing
depth below Earth’s surface. Earth’s mantle extends to about
2900 km (1800 mi), composed of substances rich in iron and
magnesium. Too much pressure to allow these to melt.The
upper levels of the mantle, called the asthenosphere, are able to
flow slowly―“plastic.”The crust is only 5–35 km thick.
Here we see a graph of depth vs. temperature. The red line
shows the melting point of the material at that depth. The
yellow line shows the temperature of the material at that depth.
So, if the yellow line is to the left (lower temperature) of the
red line, then the material is solid at that point. And vice versa,
if the yellow line is to the right (higher temperature) of the red
line, then the material is liquid at that point. As mentioned
earlier, increased pressure translates to an increased melting
point, which is why the red line through the iron core changes
temperature. At the depth of the inner core, the pressure is so
high that the melting point of iron is higher than the
temperature of the iron in the core. At the depth of the outer
core, the iron's temperature is higher than the melting point, and
so it is liquid. Above the core, the mantle is in different states
at different depths. The deep mantle is mostly solid because the
temperature is lower than the melting point of the material. At
the top of the mantle is a layer called the asthenosphere. The
material here is hotter than the melting point, and therefore is
liquid. It's a sort of plasticky liquid though, and flows only
slowly. Above that is the crust which, as you can see, is

relatively thin…only 5-35 km out of the 6400-km total depth to
the very center of the Earth.
*
Plate TectonicsEarth’s crust is divided into huge plates whose
motions produce earthquakes, volcanoes, mountain ranges, and
oceanic trenches. The shape of the ocean between the continents
of Africa and South America Similar fossils on both sides of the
AtlanticGPS satellite measure and see the two moving apart
The surface of the Earth changes because it is constantly
moving due to plate tectonics. The crust of the Earth is
composed of a number of plates, which move independently
(albeit VERY slowly). It is the movement of these plates that
causes earthquakes, volcanoes, mountain ranges, and deep ocean
trenches. How do we know this is happening? Well, one
relatively simple way is to look at the shape of the east coast of
South America and the west coast of Africa. They kind of fit.
More detailed evidence that followed from observations of this
“fit” includes the presence of similar plant and animal fossils on
either side of the Atlantic Ocean. Today, we can use GPS
measurements to quantify the movement. Incidentally, this is an
example of a major advance in science that was initially not
accepted. In fact, many geologists absolutely hated the idea
when it was first proposed. It was the evidence from
paleontologists who saw similar fossils that sealed the deal. Just
because science by its very nature is open to new ideas, doesn’t
mean that it doesn’t take a lot of evidence to truly convince
scientists, especially when it is something in their own field
that gets turned on its head.
*

The Moving Landmasses
Pangaea, Laurasia and Gondwana, leading to the arrangement
we see today
Measuring the motions of the plates, and comparing fossil
evidence, shows that the continents were initially one
supercontinent, which scientists call Pangaea. Pangaea first
split into two smaller supercontinents (which have been named
Laurasia and Gondwana). Gondwana split into the continents of
the southern hemisphere, while Laurasia split into the
continents of the northern hemisphere.
*
Seafloor SpreadingThe Mid-Atlantic Ridge, an immense
mountain ridge that rises up from the floor of the North Atlantic
OceanCaused by lava seeping up from the Earth’s interior along
a rift that extends from Iceland to Antarctica
The process of seafloor spreading explains the mechanism
driving the motion of the continents. The Mid-Atlantic Ridge is
an enormous mountain range under the Atlantic Ocean,
stretching from Iceland to Antarctica, which is caused by
material from the interior of the Earth being forced upward.
This material comes out through the volcanoes of the Mid-
Atlantic Ridge, pushing the continents apart and filling in the
gap. South America and Africa are moving apart about 3 cm per
year, as a result of seafloor spreading. Working backwards, they
must've been next to each other about 200 million years ago.
*

ConvectionHigh temperatures cause energy in the form of heat
to flow. Hot material deep in the Earth is less dense than cooler
material farther away from the core and tends to rise.As hot
mantle material rises, it transfers heat to its surroundings. As a
result, the rising material cools and becomes denser. It then
sinks downward to be heated again, and the process starts over.
This up-and-down motion is called convection.
What moves the plates? When something is hot its energy tends
to flow. We see this in a pot of boiling water, where the hot
water comes up from the bottom to the top releasing energy
through breaking bubbles, causing it to cool and sink back to
the bottom. Once back at the bottom, the heat from the stove
causes it to heat again and the cycle continues. This cycle is
called convection. Something similar occurs inside the Earth.
When there is hotter material deep in the Earth that is less dense
than material above it, it tends to rise and transfer its heat to
surrounding material. The transfer of energy cools the rising
material, causing it to become denser and sink downward again.
It gets heated up again and the process continues.
*
Plate MotionConvection currents in the asthenosphere, the soft
upper layer of the mantle, are responsible for pushing around
rigid, low-density crustal plates. New crust forms in oceanic
rifts, where lava oozes upward between separating plates.
Mountain ranges and deep oceanic trenches are formed where
plates collide.
Convection in the Earth's asthenosphere (which, remember,
flows very slowly) pushes around the crustal plates. We get new

crust in the ocean rifts, where the plates separate, and in other
places crust pushes under or over other crust where two plates
collide (these places are called subduction zones). The crust
that is pushed down at these places, is remelted and recycled
into the mantle. The crust that is pushed up forms mountain
ranges. Subduction zones can cause significant earthquakes.
Indeed, the 2004 Indian Ocean earthquake and tsunami and the
2011 earthquake and tsunami in Japan were both caused by
subduction zone activity.
*
The Earth’s Major Plates
Most earthquakes occur where plates separate, collide, or
rub together. Plate boundaries are easily identified by plotting
earthquake epicenters on a map.
Earthquakes don't only occur in subduction zones, but anywhere
that plates separate, collide, or rub together. As such, it's pretty
easy to map out the plate boundaries by plotting the epicenters
of earthquakes on a map as seen here. The red dots are the
deepest earthquakes, and the blue dots are the shallowest. The
area where you see all the red dots and most of the green dots in
a ring around the Pacific Ocean is called the Ring of Fire
because it is where the most violent geologic activity on the
planet occurs, including earthquakes and volcanoes. This area
has been the site of not only the massive earthquakes I just
mentioned, but also the recent earthquakes off of Chile, the big
quakes in northern and southern California, volcanoes in the
Pacific Northwest (Mt. St. Helens, for example) and Alaska, and
so on.
*

Plates in MotionThe plates beneath Africa and Arabia are
moving apart, leaving a great rift that has been flooded to form
the Red Sea. The plates that carry India and China are colliding.
Both plates are pushed upward, forming the Himalayas.
Here are some examples of what can be created as these plates
move. Africa and Saudi Arabia are moving apart, and the rift
that has formed between them became the Red Sea. But the
plates that carry India and China are colliding, and both plates
are pushing upward forming the tallest mountains in the world,
the Himalayas (including Mount Everest and K2).
*
Source of Earth’s Magnetic FieldThe needle of a compass on
Earth points north because it aligns with Earth’s magnetic
field.Earth’s field is produced by electric currents in the liquid
portion of our planet’s interior, our dynamo.Earth’s “bar
magnet” is not exactly aligned with the Earth’s rotation axis.A
compass needle points toward the north magnetic pole, not the
true North Pole.
Now let's move on to something that is harder to see, but the
effects of which are amazing: the Earth's magnetic field. If you
hold a compass in your hand, the needle points north because
the needle is magnetic and therefore it aligns itself with the
Earth's magnetic field. This field is created by electric currents
in the liquid part of the interior of the Earth. Because molten
iron conducts electricity, when the liquid parts of the Earth's
core move electric currents arise. A moving electric current
creates a magnetic field (just run a magnet along a power cord
that is plugged in to see this effect). This process that creates a

magnetic field from a moving electric current is called a
dynamo. Note, though, that the Earth's magnetic field is not
exactly aligned with its rotation axis. So, a compass needle is
not pointing toward the North Pole, but rather toward the north
magnetic pole. In fact, a compass needle will align with the
local magnetic field, which has some variations. Therefore,
when using a compass for navigation (especially over large
distances, as in an airplane or in an oceangoing ship), these
variations have to be taken into account. The magnetic poles of
the Earth move slowly as the motions in the Earth's core
change. Around the year 2000, the north magnetic pole was
located near Ellesmere Island in northern Canada, and has since
moved toward Russia at about 55 to 60 km per year. Another
interesting point is that the Earth's magnetic field is not exactly
symmetrical. It is offset slightly from the center of the Earth, so
if you were to draw a line between the north magnetic pole and
the south magnetic pole the line would not go through the very
center of the Earth. One final tidbit is that the magnetic field of
the Earth reverses occasionally. We can track this because as
rocks solidify they maintain evidence of the direction of the
magnetic field at the time they solidified. So we can date the
rocks using various dating techniques, and then see what the
magnetic field was at the time the rocks formed. This so-called
geomagnetic reversal occurs somewhat randomly in time,
usually between one hundred thousand and one million years
apart. The last reversal occurred 780,000 years ago.
*
The MagnetosphereMost of the particles of the solar wind are
deflected around the Earth.The Earth’s magnetic field also traps
some charged particles in two huge, doughnut-shaped rings
called the Van Allen belts.

The Sun releases a somewhat continuous stream of charged
particles called the solar wind. Because of the Earth's magnetic
field, most of these particles are deflected around the Earth. The
whole area around the Earth that is dominated by its magnetic
field is called the magnetosphere. This significantly protects
our planet as life probably would not have been able to evolve
if the surface of the Earth were constantly bombarded by
charged particles from the Sun. The pressure of the solar wind
causes the magnetosphere to become stretched out in the
direction away from the Sun, as seen here. Some of the particles
of the solar wind (and other particles released from solar
activity, which we will learn about later in chapter 9) do
manage to get through and get trapped in two doughnut-shaped
rings of radiation called the Van Allen belts (the red areas in
the diagram). What happens next is amazing to see.
*
Aurorae
If the magnetosphere becomes overloaded with particles, they
leak through the magnetic fields at their weakest pointsThe
particles collide with atoms in the upper atmosphere, exciting
the atoms to high energy levels.The atoms emit visible light as
they drop down to their ground states. The result is a beautiful,
shimmering display called an aurora: northern lights (aurora
borealis) or southern lights (aurora australis).
So, I mentioned that these charged particles from the Sun can
sometimes leak through. This mainly happens if the
magnetosphere becomes overloaded with particles, and the
leakage happens at the weakest points of the magnetic field,
which are around the two magnetic poles. The magnetic fields at
the poles enter the atmosphere of the Earth. That means that the
particles that leak in also go into the atmosphere and are able to

collide with atoms in the upper atmosphere. Now remember
from chapter 2 what happens when an atom absorbs energy. Its
electrons get excited to higher energy levels (assuming it is hit
with the right amount of energy). Since those electrons really
don't like being in those high energy levels, they will drop down
to their ground states as quickly as they can, emitting photons
in the process. In this case, those photons are in the visible light
portion of the electromagnetic spectrum. The result is what we
call an aurora (plural aurorae). When this occurs around the
north magnetic pole, it is called the aurora borealis or the
northern lights. When it occurs around the south magnetic pole,
it is called the aurora australis, or the southern lights. If you've
never gotten a chance to see this, I highly recommend trying.
The trick is that you mostly need to be at high northern or high
southern latitudes (in the United States, this translates to the
northern tier states), and then the appearance of the aurora is
also dependent upon solar activity levels.
*
Pressure and Temperature in the AtmosphereAtmospheric
pressure is caused by the weight of all the air above that
height.Sunlight heats the Earth, which heats the troposphere.
Let's now take a look at the part of Earth's systems that plays a
major role in keeping us alive: the atmosphere. The atmosphere
is an envelope of gases surrounding the Earth, and held in place
by Earth's gravity. Atmospheric pressure is the weight of all the
air above a given height. At the surface of the Earth, the
atmospheric pressure is 14.7 pounds per square inch. This
pressure then decreases as you go up in altitude. Temperature,
on the other hand, does not change so simply in the atmosphere.
In the lowest level of the atmosphere, the troposphere, the

temperature does decrease with altitude. It is heated only by
indirect sunlight (reflected off of the surface of the Earth). But
the next level up, the stratosphere, actually increases in
temperature with altitude. This is due to the presence of ozone,
which is a molecule made of three oxygen atoms rather than the
usual two. Ozone happens to be very efficient at absorbing the
Sun's ultraviolet energy. Since there will be more ultraviolet
radiation higher up (because by the time it gets lower in the
stratosphere more of it has been absorbed by the ozone), the
stratosphere is warmer at its upper layers. Above the
stratosphere is the mesosphere. There is not much ozone in this
layer, so ultraviolet radiation is not absorbed here (it passes
through to the stratosphere), and so the atmospheric temperature
again decreases with altitude. The uppermost layer of the
Earth's atmosphere is the thermosphere. The temperature here
again increases with altitude, but not because of ozone this
time. Here, the ultraviolet radiation is absorbed by individual
oxygen and nitrogen atoms. The temperature here is very high:
about 1000°C (1800°F) at around the altitude at which the
International Space Station and many other satellites orbit. This
temperature does not cause a problem, because the
thermosphere is not very dense (there’s not much “stuff” there).
Temperature is a measure of how fast particles like atoms and
molecules are moving. So the atoms and molecules in the
thermosphere are moving very fast, but they are few and far
between and the thermosphere therefore does not carry much
energy that it could transfer to satellites to damage them.
*
Convection in the AtmosphereVertical temperature variation
causes convection currents that move up and down through the
troposphere. Much of Earth’s weather is a consequence of this
convection.Convection on a grand scale is caused by the
temperature difference between Earth’s equator and its poles.

Vertical variation in atmospheric temperature causes convection
currents, much like the convection that we see occurring in a
boiling pot of water or inside the Earth. In the atmosphere, this
mainly occurs in the troposphere, the lowest level of the Earth's
atmosphere. Much of our weather results from this convection.
There is a larger scale convection (or flow of energy) that
occurs in the Earth's atmosphere, and that is a result of
temperature differences between the Earth's equator and the
poles. If Earth were stationary, warm air at the equator would
rise and flow toward the poles where it would cool and sink,
and then flow back toward the equator. However, because the
Earth rotates this convection cycle is broken up into smaller
convection patterns, which you can see in this diagram. There
are three of these patterns in each hemisphere: a tropical cell
near the equator, a polar cell near the pole, and a temperate cell
in between. These cells are the reason that prevailing winds
blow in different directions at different latitudes on the Earth.
*
Structure of the Atmosphere
This diagram just gives you an overall sense for where things
are in the atmosphere. Our weather occurs in the troposphere,
while airliners fly in the stratosphere. The ozone layer is also in
the stratosphere. And the meteors (also called shooting stars)
that we see in the night sky as well as the aurorae occur in the
thermosphere.

*
Our Sun’s
Role in the Atmosphere’s EnergyThe fraction of incoming
sunlight that a planet reflects is called its albedo.Earth also
absorbs and emits energy; the system is not in balance―the
greenhouse effect.
We've talked a little bit about the Sun's effect on the
temperature of the atmosphere, so let's look at that a little more.
In step one of this diagram, sunlight arrives at the Earth. Step 2
shows that both the clouds and the surface reflect some of the
sunlight, in fact they reflect about 30% of the sunlight. This
number, which can also be written as 0.3, is called the albedo of
Earth. The albedo is the fraction of incoming sunlight reflected
by an object. Satellite data and measurements of “earthshine”
(the light reflected off the Earth onto the Moon) have shown
albedo to vary based on cloud cover (daily and seasonally) and
latitude. The changing amount of ice cover (both at the poles
and glaciers) has also caused the average global albedo to
change in recent decades. In step 3, the diagram shows the
surface absorbing the remaining sunlight that hits it (remember
that the atmosphere, in particular the ozone in the stratosphere,
also absorbs some of the sunlight). When the surface absorbs
sunlight, the surface warms up. As we saw in Chapter 2, any
object that is heated up emits infrared radiation, and the same is
true for the surface of the Earth. The infrared radiation warms
the air near the surface, and most of the rest leaks into space.
Some of the infrared radiation, though, is trapped by the

atmosphere. There are some gases in the atmosphere (including
water vapor and carbon dioxide) that are transparent to visible
light (it shines right through them), but not to infrared. So,
when infrared radiation hits molecules of those gases (called
greenhouse gases), it partially heats the atmosphere further (and
also the surface). The temperature levels off when the amount
of infrared radiation escaping the atmosphere just balances the
amount of solar energy reaching the surface. This is called the
greenhouse effect, and without it the surface of the Earth would
be about 33°C (59°F) cooler, and Earth would be a frozen
wasteland. That’s the good side of the greenhouse effect. When
it becomes a problem is when the balance is changed. Currently,
this is happening as a result of the increase in greenhouse gases.
Since there are now more greenhouse gases in the atmosphere
than there were, less infrared radiation is able to escape the
atmosphere, so that amount is no longer in balance with the
amount of solar energy reaching the surface. The result is that
the planet is warmer. Note, the planet is warmer on a global
scale, but that does not mean it is warmer everywhere on the
planet. Note further that what I am discussing in this lecture is
science, not politics…there’s a major difference. ‘Nuff said.
*
The Biosphere
The oceans, the lowest few kilometers of the troposphere, and
the crust to a depth of almost 3 kilometers.This image shows the
distribution of plant life over the Earth’s surface. The ocean
colors show where free-floating microscopic plants called
phytoplankton are found.
All life on Earth exists in what’s called the biosphere. This
includes the oceans, the bottom few kilometers of the

troposphere, and the crust down to about 3 km. There are two
color scales in this image. The levels of chlorophyll in the
oceans mark where there is phytoplankton (microscopic, free-
floating plants). The land vegetation index shows the
distribution of plant life on the surface. The temperature of the
oceans and the atmosphere is critical for the health of the
biosphere. Even small changes can cause dramatic effects. One
example is El Niño, which is a phenomenon that occurs about
every 3 to 7 years, in which the surface temperature of the
Pacific Ocean near the equator rises 2-3°C. This warmer water
blocks the cooler water from deep in the ocean from welling
upward. As a result, the phytoplankton on the surface do not get
the nutrients they need that are normally brought up from the
deep water. Since phytoplankton are at the bottom of the ocean
food chain, when it dies off, there isn’t enough food for the
animals higher up the food chain. Other things can effect the
temperature of the biosphere, too. On a much longer time scale,
the Earth has periodically experienced ice ages due in part to
variations in the eccentricity of the Earth’s orbit and the tilt of
its axis of rotatios. These variations can cause temperature
changes on a scale of tens of thousands to hundreds of
thousands of years.
*
Human Effects on the
Biosphere: DeforestationTropical rain forests absorb significant
amounts of CO2 and release O2. 7% of the world’s land areas
with at least 50% of all plant and animal species on Earth.The
rain forests of Central America, India, and western Africa are
almost gone.To make way for farms and grazing land, people
slash-and-burn, releasing CO2 into the atmosphere.

The biosphere has also undergone another significant change
within the past 2000 years: the exponential increase in the
number of humans on the planet. The human population has
increased from around 200 million to over 6.9 billion in that
time, an increase of more than 3000%. One significant impact of
this is deforestation. Remember the diagram on the previous
page showing the distribution of vegetation across the globe?
The increased need to grow food for people (whether plant- or
animal-based food) has resulted in major destruction to the
Earth’s rain forests as they’re cut to make room for farms and
grazing land. The rain forests of Central America, India, and
western Africa are almost gone (for a dramatic example, look at
satellite images of Madagascar…over a hundred years ago,
much of the island was tropical rain forest, now the forests are
only on the eastern edge). Tropical rainforests serve a key role
in the biosphere. They are home to more than half of the plant
and animal species on Earth, despite covering only 7% of the
Earth’s landmass. Perhaps more importantly, though, the plants
there absorb carbon dioxide and release oxygen (remember the
process of photosynthesis from whatever biology class you’ve
taken?). When those plants (mainly trees) are cut down, the
carbon dioxide they had absorbed is released into the
atmosphere. Remember what carbon dioxide does in the
atmosphere? It traps infrared radiation reflected from the
surface.
*
Human Effects on the Biosphere: OzoneOzone in the
stratosphere absorbs solar ultraviolet (UV)
light.Chlorofluorocarbons (CFCs) and similar chemicals destroy
the ozone in the lower stratosphere, reducing the overall

levels.UV radiation breaks apart most of the delicate molecules
that form living tissue.
When I was discussing the stratosphere, I explained the role of
ozone (O3) in the atmosphere. It absorbs ultraviolet light from
the Sun. But ozone can be broken down by chemicals known as
chlorofluorocarbons (CFCs) and others. Over the past few
decades, there has been a marked decrease in the levels of
ozone in the lower stratosphere, especially over the south polar
region. The dip in ozone varies in size on a daily basis, but the
images here show the difference between 1979 and 2003 (darker
purple means less ozone). Where this decrease in ozone exists,
more ultraviolet light can reach the surface of the Earth, where
it damages living tissue. Note that despite the fact that you hear
about the “ozone hole” a lot, it’s not really a hole, but a
decrease in levels of ozone. Following the Montreal Protocol, a
UN treaty signed by 196 nations that called for a phased ban of
ozone depleting chemicals, the levels of ozone are expected to
recover (perhaps by 2050).
*
Human Effects on the Biosphere: Global
Warming and Climate ChangeOur understanding of climate
change is based on many different types of data.Example: The
CO2 concentration in the atmosphere has increased by 21%
since continuous observations started in 1958.The sawtooth
pattern results from plants absorbing more carbon dioxide
during spring and summer. Impact? Changes in wind patterns,
ocean currents, ice caps, ocean levels

I mentioned this briefly a bit ago, but one effect of the increase
in carbon dioxide in the atmosphere is an increase in the
average global temperature (remember, this is a global effect).
This is likely causing changes in Earth’s climate. It’s very
important to note the difference between climate and weather.
The difference is related to time. Climate is what happens in the
atmosphere over relatively long periods of time, while weather
is the conditions in the atmosphere over short periods of time.
Climate is sometimes defined as being the average weather over
a period of about 30 years. Our understanding of climate change
is based on a LOT of different data, including (among others)
temperature records, rainfall records, satellite imagery and
measurements, and ice cores (the ice traps air when it’s frozen,
so if we dig cores WAY down in glaciers, we can analyze the
atmospheric gases in those trapped air bubbles). Data from
those ice cores show natural variation in the levels of carbon
dioxide in the atmosphere, but also a significant increase since
the beginning of the Industrial Revolution in about 1800. The
data in this image shows carbon dioxide concentration just since
1958, when continuous observations began. The sawtooth
pattern is a seasonal variation. In the fall and winter, there is
less absorption of carbon dioxide by plants that lose their
foliage at that time, and then the absorption increases in the
spring and summer. But the overall slope of the graph is
upward. Again, the effect of increased carbon dioxide in the
atmosphere is that more infrared radiation will be trapped in the
atmosphere, warming it and the surface. The potential impact of
this is changes in wind patterns, ocean currents, melting of
polar ice caps, and the resultant raising of ocean levels. With
that, I will offer one more reminder that the information
presented in this lecture is based on the overwhelming majority
of the evidence, and I am not engaging in a political
discussion…only a scientific one. Next week, in chapter 6,
we’ll look at the surfaces and atmospheres of the other

terrestrial worlds of our solar system, including one that has a
runaway greenhouse effect: Venus.
*
Astronomy/Chapter6.ppt
Investigating Astronomy
Timothy F. Slater, Roger A. Freedman
Chapter 6
Exploring Terrestrial Surface Processes
and Atmospheres
Welcome to chapter 6! This week, we are going to explore the
surface processes and atmospheres of the other terrestrial
planets in our solar system: Mercury, Venus, and Mars. We will
also briefly look at one of the moons of Jupiter, as another
location of possible liquid water in our solar system.
*
Terrestrial Planet Surfaces,
the Same Yet DifferentCratersHeavily cratered areas and
smooth low-lying plainsA few thousand, evenly distributedA
few hundredHeavily cratered areas and smooth low-lying plains
VolcanoesNoneMany at hot spots, some possibly activeMany
active, primarily at plate boundariesMany at hot spots, all

inactiveAtmosphereNoneVery thickJust right!Very thin
These are the four terrestrial planets: Mercury, Venus, Earth,
and Mars. They are similar in that they are made of rock, but
they also have some significant differences. First, if we look at
the amount of cratering on their surfaces, we see two that have
some heavily cratered areas as well as smooth low-lying plains
(Mercury and Mars). Venus has a few thousand craters that are
somewhat evenly distributed across the planet. Earth, on the
other hand, only has a few hundred. Next, if we look at
volcanoes, Mercury has none, while Mars has a lot, but none of
them are active. Venus also has a lot, and they may be active.
We know, of course, that Earth has many active volcanoes
especially around the boundaries of our tectonic plates as we
saw last week. Finally, the atmospheres of these four worlds are
very different. Mercury has no atmosphere, Venus's is
tremendously thick, Mars’s very thin, and Earth's is just
right…a bit of a Goldilocks effect there.
*
Impact CratersAn impactor colliding with a body generates a
shock wave in the surface that spreads out from the point of

impact. Produces a nearly perfectly circular crater, no matter in
what direction the incoming impactor moves. Many larger
craters also have a central peak or ring of peaks.
Let's look in more detail at impact craters. These are created
when an impactor (a meteoroid, asteroid, or comet) collides
with another body. The impact generates a shockwave that
spreads out from the point of impact. The result is a nearly
perfectly circular crater, regardless of the shape or direction of
the incoming impactor. There are some examples of elongated
craters, but those are probably the result of very low angle
impacts. High-speed impacts tend to create a crater about 10 to
20 times larger than the impacting body. Also, larger craters
tend to have a central peak or (for even larger craters) a central
ring of peaks. These peaks are a characteristic of a high-speed
impact. We would not see that in a crater formed by another
process, such as volcanism.
*
Cratering Measures Geological ActivityNot all planets and
satellites show the same amount of cratering.Geological activity
erases cratering:Plate tectonicsWeatheringErosion
As we saw at the beginning of this lecture, we see differing
amounts of cratering on different planets, and also on different
moons. Geological activity, such as plate tectonics, weathering
and erosion, erases impact craters. That is why we see so few of
them on Earth compared with other bodies in the solar system.
Our Moon, for example, has no geologic activity and its surface
is covered with impact craters. The images we see on this slide
are of an impact crater on Earth (top, the Manicouagan crater in
Québec, Canada) and one on Mars. If you would like to see an

impact crater on Earth for yourself, I highly recommend a trip
to northern Arizona, where you can see the effect of the impact
of an asteroid with the Earth about 26,000 years ago. That has
not been enough time for the crater to be weathered away, and
so it is quite obvious what it is. It's about 35 miles east of
Flagstaff, Arizona, and has a whole visitor center (although you
can't go into the crater itself). The crater is nearly a mile across
and more than 550 feet deep.
*
Geology of MercuryThe Caloris Basin, a crater 1300 km (810-
mi) in diameter The impact fractured the surface extensively,
forming several concentric chains of mountains. The mountains
in the outermost ring are up to 2 km (6500 ft) high
The geology of Mercury is somewhat similar to that of the
Moon. They look very similar in images. There is an enormous
impact basin on Mercury, called the Caloris Basin, which is
1300 km across (one of the largest impact features in the solar
system). This impact must've been so large that shockwaves
traveled all the way through the planet, deforming and jumbling
the crust on the opposite side. An interesting tidbit about this
feature is that it was discovered on images returned by the
Mariner 10 spacecraft in 1974, but at the time the spacecraft
passed by part of the basin was in darkness. So, we didn't get to
see the whole impact basin until 2008 when the MESSENGER
spacecraft imaged it during its first flyby of the planet. The
MESSENGER spacecraft orbited Mercury from 2011 to 2015, so
scientists have learned a lot more about Mercury.
*

Cratering recorded gravitational shifts
in the solar system.
Cratering dropped as the solar system “cleared up” then spiked
again.
Jupiter/Saturn shifting in their orbit?
Since we are so close to our own Moon, we are able to study its
cratering history and use that to learn about the history of
cratering in our solar system. We can identify the age of craters
in different ways. For one thing, older craters often have newer
craters on or inside them. We can also use craters to determine
the age of a surface, as a surface with more craters is older than
one with fewer craters. Intense bombardment occurred in the
Moon's early history, which then decreased before spiking
upward again into a period called the late heavy bombardment.
After that, the rate of impact has significantly decreased. One
idea for a cause of the late heavy bombardment is that some
shift may have occurred in the orbits of the giant planets Jupiter
and Saturn, causing gravitational disturbances in the asteroid
belt, sending many more asteroids in toward the inner solar
system. But at this point, that is just an idea.
*
Heavy Hits During
the Late Heavy Bombardment
Some impacts were so intense they weakened the Moon’s crust,
leading to cracks where lava welled up and filled the crater.

One thing that occurred during the late heavy bombardment on
the Moon was that some impacts were so intense that they
weakened the Moon's crust, causing cracks that allowed lava to
flow up from the interior of the Moon and fill the crater. These
areas of lava flows are called mare, which is Latin for seas.
Early observers of the Moon thought that they looked like seas
or oceans, and so they gave them names such as Mare
Tranquilitatis (the Sea of Tranquility, where the first Apollo
mission landed), Mare Serenitatis (the Sea of Serenity), and
Oceanus Procellarum (the Ocean of Storms). The Moon has not
had any volcanic activity since then, and has never had tectonic
activity.
*
Tectonics on Venus: A Thin Crusty
Venus also does not have tectonic activity like the Earth.
However, it does have convection currents under its crust.
These currents are more vigorous than those on Earth, and they
prevent a thick crust from forming. They also push and stretch
the crust, so it's broken and crumpled. This model of the
activity on Venus is called “flake tectonics.”
*
A Topographic Map of VenusRadar altimeter measurements by
Magellan were used to produce this topographic map of Venus.
Flat plains of volcanic origin cover most of the planet’s surface,
with only a few continent like highlands.Why can’t we just take
pictures?

There is one big issue with learning about Venus's surface, and
that is that the atmosphere is so thick and completely covers the
surface with clouds that we cannot see the surface in visible
light. The atmosphere of Venus is actually responsible for
Venus looking so bright and beautiful in our nighttime sky,
because it reflects so much sunlight. But in order to learn about
the surface, we had to use other methods. The Soviet Union
landed two probes on Venus, which returned a few images, but
the atmospheric pressure is so great that the probes were
crushed within hours despite being built like submarines. The
other method that has been used to see the surface of Venus is
radar. Radar uses light waves in the radio band of the
electromagnetic spectrum, which can pass through the clouds,
and bounces them off the surface. Measurements of the
reflections give us radar images of the surface. This data can
also give us altimetry data, which tells us the height of surface
features. The result of this is an image such as the one on the
slide, a topographic map of Venus.
*
Tectonics on Mars: A Thick, Rigid CrustMars: no global
network of ridges and subduction zonesThe entire crust of Mars
makes up a single tectonic plate?
While Venus has a thin crust that gets broken up by the energy
of convection underneath it, Mars has a thick, rigid crust. It
does not have plate tectonics because the crust is too thick for
subduction zones to exist. So, the entire crust of Mars probably
makes up one single plate.
*

Hot Spots on MarsOlympus Mons is the largest volcano in the
solar system.The base of Olympus Mons measures 600 km (370
mi) in diameter, and the scarps (cliffs) that surround the base
are 6 km (4 mi) high. The caldera, or volcanic crater, at the
summit is approximately 70 km across, large enough to contain
the state of Rhode Island.
There is, however, evidence of past volcanism on Mars. There
are enormous shield volcanoes there, similar to the Hawaiian
Islands. A shield volcano occurs when a hotspot opens up in the
crust, allowing magma to well up from the mantle. On Mars,
because there is no tectonic activity with plates moving around,
this hotspot stayed in one place allowing the volcano to grow to
immense proportions. There are several shield volcanoes on
Mars, including a lineup of three called the Tharsis volcanoes,
but the largest of the Martian volcanoes is Olympus Mons (or
Mount Olympus). Not only is this the largest volcano on Mars,
but it is the largest volcano in the solar system. The base of
Olympus Mons would cover the state of Texas, and the caldera,
or volcanic crater, at the summit is large enough to hold the
state of Rhode Island. Despite its size, if an astronaut visiting
Mars wanted to climb it, the slopes are so relatively gentle that
it would not be impossible.
*
Valles MarinerisThe huge rift valley of Valles Marineris, 4000
km (2500 mi) long and 600 km (400 mi) wide at its center. Its
deepest part is 8 km (5 mi). This perspective image from the
Mars Express spacecraft shows what you would see from a point
high above the central part of Valles Marineris.
Mars is also home to another feature of enormous proportion:

Valles Marineris, or the Mariner Valley. This was named after
the Mariner spacecraft that discovered it. It is the largest
canyon in the solar system, 4000 km long, 600 km wide in the
middle, and up to 8 km deep! Compare this to the Grand Canyon
in the United States, which covers a portion of northern
Arizona. If the Mariner Valley were transported to Earth, it
would stretch from San Francisco to New York. The image on
the bottom shows a perspective view from the Mars Express
spacecraft. You can also search the Internet for a fly-through
video. Search for “Flight Into Mariner Valley”.
*
A Topographic Map of MarsMost of the southern hemisphere is
higher than the northern hemisphere.The landing sites for
probes on Mars are marked with an X.
Remember the topographic map of Venus made from radar
altimetry data that we looked at? Well, here's the same thing for
Mars. The fascinating thing that this shows is that most of the
southern hemisphere is higher than the northern hemisphere
(except for the Hellas Planitia). It's hard to see on this slide, but
if you look at the picture on page 148, you can see X’s marking
the landing locations of the various landers we have sent to
Mars. The future landing site of the Curiosity rover on the Mars
Science Laboratory mission is not marked here, as that decision
was only recently made. It will be landing inside Gale crater,
which is located in the lowlands of Elysium Planitia (you can
see Elysium Mons on the right side of this image). Since the
latitude and longitude are marked on this image, look for this
site at 4.6° S, 137.2° E.
*

Atmospheres surrounding terrestrial
planets vary considerably.These atmospheres all began with
materials outgassed by volcanoes.How did they become so
different?
The atmospheres of all three of these terrestrial planets (Venus,
Earth, and Mars) began with material outgassed by volcanoes.
So how did they end up so different? These diagrams are hard to
read on this slide, but you can see them on page 156 of your
book. We've already seen the one on the left, showing how
temperature changes with altitude in Earth's atmosphere. The
one in the middle shows the same graph for Venus. First of all,
notice that the clouds are significantly higher on Venus than
they are on Earth. Notice also that the pressure scale on the
right side of the diagram is different. The scale goes to one
atmosphere on the Earth graph. The atmosphere is the unit of
measure for atmospheric pressure, and one atmosphere is the
atmospheric pressure at the surface of the Earth. On Venus, that
number is 90 at the surface. In other words, the atmospheric
pressure at the surface of Venus is 90 times that of Earth. The
temperature also continuously gets hotter as you go closer to the
surface. The temperature at the surface of Venus is almost
900°F, hot enough to melt lead. Why? Because the carbon
dioxide in the atmosphere essentially traps all of the infrared
radiation that is radiated by the surface, reflecting it back down
to the surface, where it continues to heat the surface. Since
little infrared radiation can get out, this is a runaway
greenhouse effect. Venus's temperature is actually hotter then
Mercury's, even though Venus is further from the Sun. Finally,
the graph for Mars appears on the right. It also has clouds
higher than Earth's, but also some lower down. Its temperature
falls off more rapidly with altitude, and the pressure at the

surface is less than 1% that of Earth. It has about the same
percentages of carbon dioxide and nitrogen as Venus's
atmosphere, so it is also warmed by the greenhouse effect. But
the atmosphere on Mars is so thin that the greenhouse effect is
weak, and is only able to warm the surface by 5°C (compare
that to the 33°C temperature of Earth's that is attributable to the
greenhouse effect).
*
Water may have once existed
on the surface of Mars.A network of dry riverbeds extending
across the cratered southern highlands.Teardrop-shaped islands
rise above the floor of Ares Valles, carved out by a torrent of
water that flowed from the bottom of the image toward the top.
Water may once have existed on the surface of Mars. We see
dry river beds across the cratered southern highlands. Liquid
water cannot exist on the surface of Mars now, because the
atmosphere is too thin (remember it's less than 1% that of
Earth). We also see things such as the teardrop-shaped islands
in the lower image that appear to have been carved out by a
torrent of water that flowed from the bottom of the image
toward the top. Further evidence came from particular minerals
found by the Spirit and Opportunity rovers, minerals that on
Earth form only in the presence of liquid water. There is some
evidence that water may still exist under the surface on Mars.
*
Looking for Water on Our MoonSDI-NASA Clementine

spacecraft found some evidence of possible ice at the Moon’s
poles.Lunar Prospector found similar, but still inconclusive,
evidence for water.LCROSS purposefully crashed into the
Moon’s pole and caused an explosive plume of debris to be
ejected high above the surface.Water was observed among the
ejected debris.
We've also been looking for signs of water on the Moon. The
Clementine spacecraft found some evidence for water ice at the
Moon's poles. The reason it could be there is that there are some
craters at the poles that are permanently in shadow, and
therefore could stay cold enough for water ice. The Lunar
Prospector spacecraft found similar evidence, but it was still
inconclusive. The LCROSS mission purposely crashed into the
pole in order to cause an explosive plume of debris to be ejected
high above the surface so that we could look at it with
telescopes. And, in fact, water was seen in this ejected debris on
October 9, 2009.
*
Europa: What lies beneath its icy crust?Infrared spectrum shows
a thin layer of fine-grained water ice frost on top of a surface of
pure water ice.Jupiter gravitational influence cause
“squeezing,” keeping the ocean warm.
Further out in our solar system, there is the possibility of water
on Jupiter's moon Europa. To be more precise, there is water
there. The spectrum shows a thin layer of water ice frost on top
of the surface of pure water ice. But there's more to it than that.
First of all, the smooth surface of Europa is covered by dark
lines. These are fractures in the crust. Let’s look at more images
on the next slide.

*
Other Signs of an Underground Ocean
Other images (for example, the one at the top right here) show
what appear to be ice rafts moving around on the surface (image
B on page 165 shows a comparison image of ice floes on Earth).
These images clearly show that there is something liquid like
that allows the surface to move around, and also that there is
some energy moving things on Europa. Where could this energy
be coming from? Well, Europa is close enough to Jupiter that
the gravity of Jupiter squeezes Europa, heating its interior. This
could allow an ocean of liquid water to exist underneath
Europa's frozen crust. Perhaps a future mission to the Jovian
system might have radar to look through the icy crust and
search for definitive proof of a liquid water ocean on a body
other than Earth.
Next week, we will shift our attention to Jupiter and the other
giant planets of the solar system. See you then!
*
Astronomy/Lab3_Assignment_The_Moving_Constellations.doc
Monitoring the Moving Constellations
Big Idea: Sky objects have properties, locations, and predictable
patterns of movements that can be observed and described.
Goal: Students will conduct a series of inquiries about the
position and motion of constellations using prescribed Internet
simulations and learn how different stars are visible at different
times of the year in different locations in the sky.
Computer Setup:

Access http://www.heavens-above.com/ and
a) Click on CHANGE YOUR OBSERVING LOCATION link
under Configuration and set your observing location and time
zone(My location is Crestview, FL Central Time Zone). If you
use the search feature, you should just be able to click “Update”
at the bottom of the screen.
b) Click on INTERACTIVE SKY CHART link under
Astronomy
c) NOTICE that the star charts are set such that north is toward
the top and west is to the right, which is different than a map of
the United States.
Phase I: Exploration
1) When you first turn on the star map, the yellow star marking
the Sun may be visible. If you were to go outside right now,
could you see these stars shown on the map? Explain why or
why not.
2) If the yellow star marking the Sun is not visible, change the
time until it is. Which constellation of stars is the Sun closest
to?
3) If you increase the time by one hour, remembering to use a
24-hour clock, toward which direction does the Sun move?
Highlight or underline one: North South East West
4) Now, 1 hour later than when you started, which constellation
of stars is the Sun now closest to?
5) If you advance the time to sunset, which constellation of
stars is the Sun closest to at sunset?
6) Advance the time to sunrise, which constellation of stars is
the Sun closest to at sunrise?

7) What generalization statement, in a complete sentence, can
you make about how the Sun and the stars appear to move
together in the sky?
8) What is the physical cause of your generalization (what is
happening physically in the world that causes what you see)?
Phase II – Does the Evidence Match the Conclusion?
9) Set the star map to noon today. If you could see the stars
hidden behind the brilliantly shining Sun, which constellation of
stars is the Sun closest to?
10) Using the sky chart, which constellation of stars is the Sun
closest to tomorrow?
closest to one week later?
closest to two weeks from now?
closest to three weeks from now?
closest to one month from now?
closest to two months from now?
closest to three months from now?
closest to six months from now?

closest to nine months from now?
closest to one year from now?
closest to two years from now?
21) If a student proposed a generalization that “the
constellations seem to slowly drift westward compared to the
position of the Sun, with the Sun covering constellations at a
rate of about one per week,” would you agree, disagree with the
generalization based on the evidence you collected? Explain
your reasoning and provide evidence either from the above
questions or from evidence you yourself generate using the star
map program.
Phase III – What Conclusions Can You Draw From the
Evidence?
Orion is a prominent constellation visible in the winter time,
usually being hidden by the shinning Sun in the summer. What
conclusions and generalizations can you make from the
following data collected by a student in terms of how the
WHEN IS ORION VISIBLE DIRECTLY ABOVE THE
SOUTHERN HORIZON? Explain your reasoning and provide
evidence to support your reasoning.
Date
Time
above Southern Horizon
Azimuth (west = 270()
Direction
October 1

6:00 am MDT
180(
South
November 1
4:00 am MDT
180(
South
December 1
1:00 am MST
180(
South
January 1
11:00 pm (2300) MST
180(
South
February 1
9:00 pm (2100) MST
180(
South
Evidence collected in standard time from http://www.heavens-
above.com/ for Laramie, WY
22) Evidence-based Conclusion:
Phase IV – What Evidence Do You Need?
Imagine your team has been assigned the task of writing a news
brief for your favorite news blog about when one of your team
member’s horoscope birth sign is covered by the Sun. Describe
precisely what evidence you would need to collect in order to
answer the research question of, “Over what precise period of
time is my horoscope birth sign being covered by the Sun and is
thus unable to be observed?” Your procedure MUST use this
heavens-above.com web site, you do NOT need to use any other
resources. You do not need to collect data for this phase, but
you should write the instructions such that someone else could

follow your instructions to successfully collect the relevant
data.
23) Create a detailed, step-by-step description of evidence that
needs to be collected and a complete explanation of how this
could be done—not just “look and see when the Sun is nearby,”
but exactly what would someone need to do, step-by-step, to
accomplish this.
Phase V – Formulate a Question, Pursue Evidence, and Justify
Your Conclusion
Your task is design an answerable research question, propose a
plan to pursue evidence, collect data using heavens-above (or
another suitable source pre-approved by your lab instructor),
and create an evidence-based conclusion about some motion or
position in the sky for the constellations that you have not
completed before. This question doesn’t need to be complex.
Think about the observations you’ve learned about so far in the
lab. The best research questions are those that can’t be
answered by a simple yes/no, or a single number or
characteristic. Look at ways you can compare/contrast or
otherwise analyze a collection of data. The questions in phases
II through IV are good examples. Your question can be similar,
but must be different from those. If you have difficulty, ask
your instructor.
Research Report:
24) Specific Research Question:
25) Step-by-Step Procedure to Collect Evidence:
26) Data Table and/or Results:
27) Evidence-based Conclusion Statement:

Phase VI – Summary
PRINT YOUR NAME
1) Create a 50-word summary, in your own words, that
describes which constellations are visible at night and how this
changes over the night and over the year. You should cite
specific evidence you have collected in your description, not
describe what you have learned in class or elsewhere. Feel free
to create and label sketches to illustrate your response.
5
Astronomy/Thumbs.db

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