Transcript Mars Mystery Rocks

Using Reflectance Spectrometry to Identify
Compositions
Credit: NASA/JPL-CalTech/LANL
Credit: NASA/JPL-CalTech
How Do We See Mars?
 Our eyes, cameras, and mission
instruments use the sunlight
reflected off its surface.
Spectra Are “Fingerprints”

Fingerprints can be used to identify individual people
Credit: http://www.moillusions.com
Credit: http://math-blog.com
Credit: http://www.vetmed.vt.edu
Spectra Are “Fingerprints”

Spectra are unique to elements and minerals

Used to identify minerals; rocks
Credit: ChemCam/LANL/IRAP/CNES
Credit: Univ. of Toronto
Types of Spectra
Credit: http://csep10.phys.utk.edu/astr162/lect/light/spectra2.gif
Using the ALTA to take a Spectrum
 These rocks are “Mars” rocks that you—like a rover on a mission—
are analyzing. Your task it to determine their possible compositions,
by comparing the Mars rocks’ spectra to known Earth rocks’ spectra.
Credit: Ward’s Scientific
Using the ALTA to take a Spectrum
 These rocks are “Mars” rocks that you—like a rover on a mission—
are analyzing. Your task it to determine its possible composition, by
comparing the Mars rocks’ spectra to known Earth rocks’ spectra.
 Buttons on front, LEDs & detector on the back
 Push each button on the front and see what happens on the back
Using the ALTA to take a Spectrum
 What is the ALTA doing?
 Light from diode strikes the surface of the sample
 Light reflected off the sample enters the detector
 Read-out on the front indicates how much of the light has
been reflected (voltage)
 Because each ALTA has its own sensitivities, the read-out
should be compared to the reflectance of white paper
Taking the Dark Voltage
 What happens if you place the ALTA down flat and don’t
turn on any of the lights?
 You still have a number - ALTA’s photodetector and
electronics don’t go to zero. This is your “Dark Voltage”
Using the ALTA to take a Spectrum
 Need a large flat surface if possible.
 Try not to let outside light into the detector.
 Work in groups of 4; one can hold the sample and ALTA,
one can press the buttons, one to record the data, etc.
 Begin with taking the data for two stacked pieces of white
paper.
Terrestrial Spectrum #1
Terrestrial Spectrum #2
Terrestrial Spectrum #3
Terrestrial Spectrum #4
Terrestrial Spectrum #5
Terrestrial Spectrum #6