Surface Temperature, Elevation, Sun Angle

• to introduce you to Planetary Fourier Spectrometer (PFS) derived data on surface temperatures
• to give you practice in inferring patterns among factors that partially drive Martian weather
• to give you practice in Excel graphing

The PFS carries the Long Wavelength Channel instrument, which collects spectra from a wide array of infrared wavelengths (1.2 - 45 microns). The PFS will focus on minerals in Martian dust, pressure measurements for CO² by measuring the 15 micron CO² absorption band, and infer surface temperatures by noting the peak emission wavelengths from the Martian surface and applying the Wien Displacement Law. This last function is the source of the data for this lab, taken from ESA's Mars Express' 399th orbit on 1 May 2006. The data are presented in graphical form each week by the European Space Agency, and I turned the graphical data into tabular data for this lab.

Your data

You can download your data from https://home.csulb.edu/~rodrigue/mars/labs/PFStemperature.xls. This is an Excel database, which you can save on your portable storage device or on the scratch drive in the lab (where you should create a folder for yourself so you can find your data easily). Remember the scratch drive is normally cleaned out once a week, so you do need to transfer your work to your own storage device.

The data are presented in four columns:

• Latitude (note that southern hemisphere latitudes are given as negative numbers and northern hemisphere latitudes are given as positive numbers)
• Sfc Temp K means surface temperatures in Kelvins (the freezing point of water at sea level on Earth is 273 K, and the boiling point is 373 K -- comfortable room temperatures would be 293K - 298 K or so).
• MOLA elev (m) is derived from the NASA Mars Orbiter Laser Altimeter and is presented in meters above or below the Martian geoid, which is used there in lieu of mean sea level)
• Sun angle is the angle that the sun makes with the horizon at the point directly below the orbiter (the spacecraft's nadir). This is a function of latitude, the sun's declination (on Mars, that can range from +25° or 25° N to 25° S), and the time of day the spacecraft passes overhead.

Graphing the data

Make three line graphs. Each will have latitude +30 as the X axis. For the temperature chart's Y axis, make sure that its scale ranges from 200 to 270 K. For the sun angle chart's Y axis, make sure to format the scale to range from 30 to 60 degrees. For the elevation chart, make sure the Y axis is scaled to a range from -4,000 m to +2,000 m. You also want to format the three graphs so that they are the exact same size, so that you can stack them above one another to look for patterns. By formatting them this way, you'll be able to compare the three charts, latitude by latitude, to look for patterns and anomalies. You might want to experiment with Excel's formatting options to make them attractive.

Lab report

Your graphs in hand, write a brief lab report answering the following questions:

• Which of the two factors is likelier to be the big driver of temperatures on Mars as much as on Earth?
  • Is that what you see in general?
  • What about any anomalies or departures from that relationship? Where do they occur?

• What would you predict the effect of the other factor would be on the core relationship?
  • Do you see any signals in the data that indicate the effect of the second factor?
  • Where? How influential does it seem?

• the vertical temperature structure of Mars atmosphere during Orbit 399, which you can access here: http://www.pfs-results.it/typo3temp/pics/d1a1f6fe3f.gif.
• Something else collected during that orbit that might be relevant is dustiness, at http://www.pfs-results.it/typo3temp/pics/14417aec29.gif.