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09 January 2004

Science Notebook: Analyzing Images and Data from Mars

by Forrest M. Mims III
www.forrestmims.org

Geronimo Creek Observatory
433 Twin Oak Road
Seguin, TX 78155
Phone: 830-372-0548

Extracting usable scientific information from images and data returned to Earth from the surface of Mars might seem far beyond the capabilities of amateur science. Actually, there are a number of useful science projects and exercises that a careful observer can perform.

Consider those remarkably detailed color images of the sandy plain around the Mars Exploratory Rover Spirit landing site returned to Earth shortly after the craft touched down on January 3, 2004 (see www.nasa.gov).

The surface of Mars adjacent to the Spirit landing craft on January 6, 2004. Photograph courtesy of NASA's Jet Propulsion Laboratory. Click image to enlarge.

The rocks in these images are smaller and less abundant than images sent back by the two Viking landers and Pathfinder. Some of the rocks are smooth, while others have obviously angular features. There are subtle color differences among the rocks.

NASA and university scientists will study this and more in great detail. So can we.

What is the range of angles of the angular rocks? How does their color compare with the smooth rocks? How does the color of the soil and rocks compare with that in the Viking and, especially, the Pathfinder photos? How can you be sure that the color in the images is "real" and comparable? In other words, have the images been filtered to remove excessive red sunlight scattered by the dusty sky?

As for the sky, it can also be studied. When the solar panels of Spirit were first exposed to sunlight shortly after landing on Mars, Jennifer Trosper, Spirit's mission manager for surface operations at the Jet Propulsion Laboratory, noted that the panels were providing only 83 percent of the expected power. More than expected dust in the martian atmosphere apparently caused the solar panel's reduced output.

The solar panel's reduced output was double the loss I measured using a solar cell here at my observation site in Texas during the maximum stratospheric aerosol period that followed the eruption of Mount Pinatubo in 1991. Yet present conditions on Mars are relatively benign when compared to the planetary scale dust storms that sometimes veil the planet. I measured a reduction in temperature associated with the Pinatubo eruption or more than a degree Celsius. How much do the martian dust events modulate the temperature of that planet?

Some of the high resolution horizon images from Mars show obscured features on the horizon. These images can possibly be related to horizontal visibility. Especially helpful in this regard are daily weather reports from spacecraft in orbit around Mars that provide information about clouds and dust storms. The weather report during the landing of the Mars Exploration Rover on January 3, 2004, (www.msss.com/mars_images/moc/mer_weather/weather/27.02.Jan.04.MER.html) even included the aerosol optical depth (0.41 +/- 0.07).

Atmospheric data like these and sky images provide important clues about the variability of the martian sky. There are even incredible images of martian sunsets and twilights that can be used in this role. Just as fascinating are images that show dust devils on Mars and the sinuous tracks in the orange soil they leave in their wake. Dust devil tracks crisscross the Mars Exploratory Rover Spirit landing site.

It's very important, of course, to study what professional scientists have done before drawing any conclusions about your analysis of Mars data. For example, an excellent paper on the optical properties of the martian sky is P. H. Smith, et al., Results from the Mars Pathfinder Camera, Science 278, 1758-1764, 1997, which is available at www.sciencemag.org/cgi/content/full/278/5344/1758. Many other papers and reports about the Viking, Pathfinder and Mars Exploratory Rover missions can be found by searching the web.

I recommend using a good search engine for best results, for martian images and data can be found on many web sites. This is especially a good idea when the NASA web sites are clogged by traffic during ongoing Mars missions.