From: jwee@mail.arc.nasa.gov (Jan Wee)
Subject: Live From Mars Teacher's Guide Preview: Activity 1.3
Date: Fri, 04 Oct 1996 15:29:21 -0500
Dear discuss-lfm members,
For your preview....
Jan Wee
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Activity 1.3: Follow that Water - Investigations with Stream Tables
Teacher Background
Water is essential to life on Earth: its abundant presence on our
world drives the weather and shapes the land by rain, runoff and
erosion. Whenever we see what looks like evidence of liquid water
elsewhere in the Universe, we become especially interested, since
water is requisite for life.
In the late 19th Century astronomers peered at Mars through
telescopes and saw lines stretching across its surface: Giovanni
Schiaparelli, an Italian, called them "canali" , or "canals" in English.
Some interpreted these "canals" as evidence of intelligent life, and
even an advanced Martian civilization capable of massive, planet-
wide engineering projects. Now spacecraft have looked close-up at
Mars, and we know there are no canals built by a Martian Corps of
Engineers. But some of the channels do have shapes which look much
like those we see on Earth. While it's tempting to think of them as
dried-up river beds, most scientists think many of the channels
resulted from massive floods, or groundwater seepage, rather than
from sustained rainfall and enduring rivers. How do we know we're
not fooling ourselves, or misinterpreting the data, as did some of
those 19th century observers?
Scientists use different methods to understand the conditions under
which the channels may have been formed. One method involves the
use of stream tables, to simulate different rates of flow, from
gentle rivers flowing for a long time, to sudden, massive floods. In
this Activity, students will have the chance to discover for
themselves some of the characteristic shapes created by differing
volumes of water, flowing at different rates ("volume over time").
With "educated eyes" they can then turn to study images of Mars and
recognize the features and discuss the mechanisms which might have
caused them.
Objectives
Students will work in teams to build simple stream tables and other
needed equipment.
Students will vary the angle of the stream tables in order to
simulate different flow rates and compare the results.
Students will observe various features formed in a stream table by
flowing water and compare these model features to photos of real
features on Mars in order to make inferences about the possibility of
water channeling on Mars.
Materials (for each team of students)
Please note: if these materials are difficult to secure, consider using
only one set for the entire class, and assigning a different Planetary
Geologist team per angle, and emphasizing the Image Processing and
Data Analysis process for those who must watch. Although there will
be less student hands-on time, it might be better to do the Activity
in this way rather than foregoing it altogether, so important is the
issue of water to Martian science and mission planning.
* Activity 1.3 Student Work Sheet
* 1 wallpaper tray (poke hole about size of a quarter in one end
so water can drain into a bucket)
* metric ruler
* two buckets of clean play sand
* a third empty (catch) bucket
* a one gallon plastic water jug
* measuring cup
* 2 plastic funnels: one with a 1/4 in. opening and one with a 1/2
in. opening
* several blocks of wood cut from 2 x 4s, each about 6 inches
long
* a protractor
* a piece of string and a small weight
* a couple of stones that are flat on top and bottom, about 1/2 to
1 inch in diameter and 1/2 to 1 inch high
* plastic lids from 1-liter soda bottles
* selected images of Martian surface features
* selected images of Earth, featuring dry river beds (NOTE: The
LIVE FROM MARS videos will feature such images. More may be found
in the slide set and Explorer's Guide to Mars poster, all included in
the LFM Teacher's Kit.)
Vocabulary
avalanche
delta
erosion
flow patterns
geologist
meandering
outflow channels
simulation
topographical map
Engage
Show students pictures or video of rivers and floods on earth
(perhaps local occurrences in your region). Do they think such
conditions could exist on Mars today? Ask if they think Mars could
ever have had liquid water. Or consider the question of water on
Mars through a discussion on the possibility of life on Mars today in
contrast to the distant past. Discuss conditions that seem necessary
for life to develop. Cite the August 1996 announcement of the
possible discovery of ancient Martian life in a meteorite.
Explore / Explain
Procedure
Please note: some details are provided on the Student Work Sheet and
its diagram, which you should review along with this procedure.
1. Distribute materials to each student team. Explain that each
team is going to work as Planetary Geologists to investigate what
can happen to a surface when water flows across it, and that they
will share their data to come up with some principles by which
water shapes landforms in specific ways.
2. Demonstrate stream table set up and use of the protractor to
align the stream table at a given angle. The demonstration stream
table should be set at an angle of 5 degrees.
Pour 1 quart of water into the 1/4 inch funnel and allow the water to
run down the tray through the groove as the teams watch. Have
students describe and sketch the flow pattern which results,
carefully noting such things as: the shape of the flow pattern
including
whether the channel cut by the water was straight or curved;
how wide the channel became;
how deep the channel became;
how long it took for the jug to empty;
whether a small or large amount of sand was carried down stream by
the water;
whether or not avalanching occurred, and
whether or not a delta was formed.
3. Assign each team a slant angle (from 5 to 25 degrees) and
allow time for basic set up. For the first set of trials, each team
should use the plastic funnel with the 1/4 in. opening. Teams should
complete Trial # 1 and record results on STUDENT WORKSHEET.
4. Before continuing, allow time for teams to contrast and
compare the stream tables set at different angles. Discuss.
Teacher Background
Students will see that at angles of about 15 degrees and higher, the
sand will wash out. Larger volumes of water over shorter time
periods (e.g. flood conditions) carve deeper channels with steeper
sides. Only at angles of around 5 degrees, simulating gentler
processes (e.g. slower flow over longer times) does the water begin
to create curves and meanders more typical of terrestrial rivers.
Remind students that most stream beds have slopes that are
typically 5 degrees or less but that in this simulation the angle
stands for flow rate, not the underlying topography of the planet.
Also note that, as in most simulations, you can't replicate all
aspects of the original condition you're trying to understand: for
example, results obtained by using sand do not perfectly model rivers
running through soil or over rock. But varying the angle does simulate
flow rate, one key variable scientists think important for Mars.
5. Smooth the damp sand back uphill to a uniform layer. Then
repeat the same experiment at the same tray angle, but this time
using the funnel with the 1/2 inch opening. Repeat STEPS 3-4.
6. Again, smooth the sand back uphill. Repeat the experiments, but
this time tell students to place the stones and the small bottle lids
in the tray in such a position that the stream of water will encounter
them, working them into the sand and adding a thin layer on top. (This
simulates what happens when flowing water meets the elevated rim
of an impact crater.) Have students carefully observe and record the
appearance of the patterns in the vicinity of the glass and stones at
the end of the experiments.
7. Challenge students to answer the following questions:
At what slope angles (flow rates) do meanders and deltas occur?
At which slope angles (flow rates) does the sand wash out
completely?
How does the slope angle (flow rate) affect the amount of sediment
deposited down stream?
What kinds of things happen to the sand immediately after the water
starts flowing?
What kinds of things happen to the sand after the water has flowed
for awhile?
What effect does the volume of water that flows per second have on
all of the above?
8. As a last activity, simulate a large scale catastrophic flood by
filling the gallon jug with water and carefully creating a uniform
"waterfall" along the top of the stream table. Have students try with
and without the stones and bottle lids in the flow. Again record and
discuss results.
9. Finally, distribute copies of the Viking images of Mars. Ask
students to look carefully at each one and challenge them to compare
examples of the different types of patterns they created in their
stream table experiments with what they see in the actual images of
Mars. Ask them to draw conclusions about the presence of water on
Mars in the past and to draw general conclusions about the differing
amount and rate of flow of water in the various areas on Mars seen in
the images.
SIDEBAR: (WE NEED TO GIVE A THUMBNAIL DESCRIPTION OF SPECIFIC
PLACES WE EITHER SEE IN THE VIDEO, OR ONLINE, OR IN THE GUIDE, OR
IN THE KIT.)
Ask them to search for signs of liquid water on Mars in the Viking
images (i.e., on Mars today). Challenge them to hypothesize where
they think all the water went.
Expand/Adapt/Connect
Research the various theories as to how water was released onto the
Martian landscape at various times in the past and where most
scientists think it is today. (Cross reference the Martian polar caps
as well as the appearance of certain craters such as Yuty.)
Have students examine a map showing the geological surface
features over the entire surface of Mars. Have them mark the
location of outflow channels. Have them do the same with the
location of valley networks. Ask them to describe the differences in
their geographical distribution and challenge them to explain the
reasons for this.
Provide students with the prime landing site for Pathfinder as well
as the coordinates of the Viking 1 and 2 landing sites . Ask students
to describe these locations relative to the location of outflow
channels and valley networks. Challenge them to hypothesize why
scientists chose these particular locations to put spacecraft down on
the surface of Mars.
Research meandering streams. What is an oxbow lake and how is it
formed? Why does a river bed change over time? Compare and
contrast each terrestrial feature to landforms on Mars.
Go online and download Mars images. Create a visual display
illustrating the various landforms on Mars. If you or your students
have documented the flow table experiments, prepare poster displays
relating flow rate to surface feature (and submit to PASSPORT TO
KNOWLEDGE online or in hard copy!)
Language Arts: Read about Giovanni Schiaparelli. Compose a letter
he might have written (or emailed) to NASA regarding his concerns
about the veracity of new data coming from Mars.
Write a news article about the stream bed simulations and report on
your data.
Math: Noting the scale of the map, have students measure and
calculate the area of some prominent outflow channels. Compare
these areas to related places on Earth such as the Nile River Valley,
the channeled Scablands region of Washington State or an area of
their home state.
SOCIAL STUDIES: Research the Scablands region of Washington State.
Suggested URLs
http://www.msss.com/http/ps/channels/channels.html
http://nssdc.gsfc.nasa.gov/planetary/viking.html
http://www.jsc.nasa.gov/pao/flash
Note: this Activity is adapted from materials and concepts developed
during workshops held by JPL's Mars Exploration Directorate, as part
of its Education and Outreach Initiative, (Meredith Olson, Project
Educator.) Related Activities may be found in the series of Student
and Teacher Publications created by JPL: to order, contact TERC at
617.547.0430. The first two modules and a set of Mars images are
part of the LFM Teacher's Kit (to order see page CHECK.) LFM thanks
Dr. Olson for her review of this adaptation of the original activity.