What feature of the light source do the spectra represent? In other words, what is it that you are actually analyzing? Why do you think spectrometers are so valuable for studying celestial objects?

Water on Mars & Light from the Stars

Introduction

Welcome to the final lab activity of GEO 101C! In the first part of this week’s lab, we will leave Earth behind and venture to our neighboring planet of Mars. Using Google Mars, we will explore the terrain of the Red Planet, looking at evidence of past water flow across its surface. In the second part of the lab, you will build a spectrometer, a device for observing the spectra of different light sources.  Spectrometers enable astronomers to determine the composition of distant stars, as well as how far away they are from us. Before beginning this lab, take a few minutes to review the list of materials required to complete Part 2, on page 6.

Your final product for this lab will be a lab report.  It is not necessary to submit this worksheet.  Your report should cover all of the questions you have answered here (in paragraph essay form, not question and answer format). It should discuss how these two tools – Google Mars and spectrometers – can be used to study distant places (planets and stars).    

Part 1:  Water on Mars

Begin by clicking here (Links to an external site.) to open the website containing the location files you will use this week.  Under “Other Materials”, click on “Placemarks – Mars Fluvial Features” to download the file to your computer. Once it is downloaded, open it, and it should open automatically in Google Earth Pro.

Once Mars appears, you’ll have a different set of layers from Google Earth to explore. The Global Maps layer can be used to change the surface layer (you may have to expand this folder to see these options): use the radio button to choose the layer and click the blue layer name to bring up a brief description of that dataset. The “Visible Imagery” contains the highest quality images, but the Viking Color Imagery layer is more uniform and may be easier to use in some places. The Daytime Infrared, Nighttime Infrared, and Colorized Terrain are interesting to explore but will not be used here.

1. Locate the volcano Apollinaris Mons (also called Apollinaris Patera). The placemark is located on one side of the caldera: zoom out so you can see the flanks of the volcano as well.
   1. Describe the linear features that surround Apollinaris: if these were stream channels, what type of drainage would this be? Which one fits the features around Apollinaris the best?  Include a simple sketch of the drainage below; take a digital photograph of your sketch to include in your lab report.
   2. Consider the material that makes up Apollinaris: what does the presence of these linear channels suggest about the strength (ability to resist erosion) of the underlying material? Suggest an appropriate composition for this material as part of your answer (note the brief description given of Apollinaris in the instructions above.)
2. Locate the feature Warrego Valles. This question is best answered using a “eye alt” of about 200 km/120 miles – set your zoom level so the eye alt value in the lower right corner of the window is about 200 km or 120 miles.
   In the space below, sketch the general shape of Warrego Valles. Take a digital photograph of your sketch to include in your lab report. What type of drainage does this appear to be – and what implications does this have for how Warrego Valles might have formed?
3. Locate the crater Orson Welles and examine the valley that starts at the crater’s NE rim (Shalbatana Valles). Briefly describe the valley below. Include a simple sketch of the valley; take a digital photograph of your sketch to include in your lab report.Identify any evidence of erosion/deposition in the valley floor and suggest a process by which this valley may have formed.
4. Locate Noctis Labyrinthus (this feature is on the western edge of Vallis Marineris, the “Grand Canyon of Mars”).
   1. Assume that water has flowed through this area: what type of drainage pattern is present here? Include a simple sketch of the drainage; take a digital photograph of your sketch to include in your lab report. 
   2. What does this type of drainage pattern suggest about the underlying bedrock?
5. Locate the “Feature in Eberswalde”, and zoom to an “eye alt” of 11 miles / 18 km with the placemark in the center of the window.
   Sketch the feature below and suggest how it may have formed (this is very much a mystery, with no right answer). Take a digital photograph of your sketch to include in your lab report.

Part 2:  Light from the Stars (Building a Spectrometer)

The instructions below describe how to build a spectrometer. Here is a link if you wish to view the site where the instructions are from.

Materials needed:

• A CD or DVD that can be sacrificed to this project. Old software CDROMs work great.
• A cereal box. Any size that can hold a CD or DVD disk will do.
• A sharp knife or razor blade to cut into the cereal box.

Our spectroscope has three main parts. There is a slit made from a razor blade to make a path for the light, a diffraction grating made from a CD disk, and a viewing port.

To construct your spectroscope, you need to put a slice in one side of the box at roughly a 30-degree angle. This will hold the CD. Place the CD in the slot to determine where to place the other two cuts. On the top of the box, cut a hole about half an inch to an inch square above the CD. On the side opposite the CD, make a very narrow slit opposite the CD. Alternatively, you can cut a larger slit, and cover it with 2 pieces of foil to control the size of the slit. Spectroscope complete!

Photograph your finished spectrometer and include the photo in your lab report.

Once you have assembled your spectroscope with the instructions in the lecture and above, use it to examine the spectra of three different light sources. Make sure that at least one of them is the sun or moon, but the others can be incandescent lights, compact fluorescent bulbs, LED lights, halogen or xenon bulbs, televisions, computer screens, candles, fireplaces, etc. Aim the slit towards the light source you are investigating, then look through the viewing hole to see the spectrum on the disk.

Answer the following questions:

1. Identify each light source you viewed and describe the spectra you observed from that source.  For each description, include colors, if the colors are blended together or separated, and if the colors are fuzzy or distinct.
2. What feature of the light source do the spectra represent? In other words, what is it that you are actually analyzing?
3. Why do you think spectrometers are so valuable for studying celestial objects?

Part 3:  The Report

Write up your lab in a well-crafted report.  The report should cover all the questions from Part 1 and Part 2, along with photos of all of your sketches from Part 1 and of your completed spectrometer in Part 2.  Also include a discussion of how these two tools for studying distant worlds, Google Mars and a spectrometer, enable us to make new discoveries.