Interpreting Data from Mars
Here is a compilation of all the Mini-TES data released to the public:
A brief overview of how to read these data:
Some of the "squiggly-line" graphs tell how much radiation at a certain wavelength or wavenumber. The y-axis (vertical axis) tells us the emissivity, or "how much" radiation is coming out of the sample. On the x-axis (horizontal), we can tell at what wavelength or wavenumber that the emission data was recorded. The x-axis is labelled in both wavelength and wavenumber because it might be better to choose one over the other when comparing to other data. Wavenumber is simply 1 divided by the wavelength. Note, however, in this case, that wavelength was in micrometers and wavenumber is in centimeters-1, so you must convert your units carefully.
Every mineral has its own thermal emissivity "signature" or spectra. Think of it as its own DNA sequence. Each sort of chemical bond in a mineral will emit distinctive radiation at a certain wavelength. And if you know exactly what a pure mineral's spectra is, and your rock's spectra looks awfully close to to it, chances are that your rock is composed largely of that mineral. Now, in a rock, there might be tens of minerals that appear in your spectra, and it makes the job of identifying minerals much more harder. But those key "squiggles", where you see a big dip or a characteristic squiggle, helps you to determine what your rock is made out of.
The Mini-TES takes thermal pictures on Mars. Instead of capturing light, as we do with our own eyes, it captures heat, or more appropriately thermal radiation. A scientist then assigns a colour to each temperature and then places them on a map. What's with all the circles, though? Think of Mini-TES as a digital camera with a really big pixel size. Unlike the Pancam, which has a high resolution, Mini-TES just takes one temperature measurement with each picture. While a visible light image with a giant pixel size (i.e. big blocks of colour) wouldn't tell us much about Mars, broad thermal measurements can tell us a lot about what the rocks are made of.
Now take the spectra on the right for example. Each thermal reading is one circle on the map. That is the average temperature in that circular area. Dust (in the upper part of the image) usually holds in more heat, and so is warmer than the surrounding area. It is assigned a red colour. But note that dark blue circle near the bottom left. Mini-TES has centered in on a large rock. Individual rocks tend to be cooler than dust, and since that rock takes up most of Mini-TES' field of view, it records a lower average temperature, and the scientists have assigned it a blue colour.
Now you're ready to analyze some of the data from Mars:
Phil Christensen discusses the hematite "blueberries" (*.asx file - Discovery Channel Canada)
Rover Press Briefing with Phil Christensen (RealVideo file)
Also, visit Mini-TES' website at: http://minites.asu.edu/latest.html
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Page content written by Stephanie Wong.
21 March 2004
© 2004 - imagiverse Educational Consortium