Robot Explorers: US Unmanned Space Missions: page 25
The 2001 Mars Odyssey is part of NASA's Mars Exploration Program, a long-term effort of robotic exploration of the red planet. The opportunity to go to Mars comes around every 26 months, when the alignment of Earth and Mars in their orbits around the sun allows spacecraft to travel between the two planets with the least amount of energy. 2001 Mars Odyssey launched on April 7, 2001, and arrived at Mars on October 24, 2001.

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Artist's rendering of Odyssey at Mars.

Odyssey's prime mission will run from February 2002 through August of 2004. Odyssey's goal is to map the amount and distribution of chemical elements and minerals on the surface of Mars. Odyssey will look specifically for hydrogen in the form of water ice just beneath Mars' surface. In addition, the spacecraft will be studying the amount of radiation in the low Mars orbit in an effort to determine the radiation-related risk to any future human explorers who will one day go to Mars.

In April the orbiter reached an important milestone: a full Mars year (687 Earth days) of science mapping. During this Martian year, it has already:

1. shown us where water ice lies buried beneath the surface

2. analyzed "what Mars is made of" by identifying minerals and chemical elements

3. studied the Martian radiation environment to help us understand potential health effects on future human explorers
Odyssey has three primary instruments:
  • THEMIS (Thermal Emission Imaging System), a camera that images Mars in the visible and infrared parts of the spectrum in order to determine the distribution of minerals on the surface
  • GRS (Gamma Ray Spectrometer), a spectrometer that uses the gamma-ray portion of the electromagnetic spectrum to look for the presence of twenty chemical elements on the surface of Mars, including hydrogen in the shallow subsurface
  • MARIE (Mars Radiation Environment Experiment), an energetic particle spectrometer for studying the radiation environment

Spectrometers are instruments that allow scientists to collect data that would otherwise be invisible to us. Our eyes are sophisticated detectors that can reveal much of the world around us, but they are only sensitive to a very small part of the electromagnetic spectrum that characterizes light.

We call the part of the electromagnetic spectrum that we can see "visible" or "optical" light. To fully appreciate the complexity of the world around us, however, we need to rely on human-made devices to provide views of the "invisible" world -- that is, the parts of the electromagnetic spectrum we cannot see without the aid of technology: gamma rays, X-rays, ultraviolet waves, infrared waves, microwaves, and radio waves.

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Image taken with THEMIS in infrared, which shows the varying surface temperatures of Mars.
odyssey-spectra.jpg (7083 bytes) Spectrometers work by spreading light out into its different wavelengths to create spectra, which look something like rainbow-colored bars. Within these spectra, scientists can study the emission and absorption lines that provide "fingerprints" of any atoms and molecules that may be present. Each atom has a unique fingerprint because they each can only emit or absorb certain energies or wavelengths. That is why the location and spacing of spectral lines--the fingerprint--is unique for each atom. Spectrometers are the instruments that engineers build to detect these kinds of fingerprints.

This graph at right shows the first results of the study of the radiation dose equivalent as measured by Odyssey's Martian radiation environment experiment at Mars and by instruments aboard the International Space Station, for the 11-month period from April 2002 through February 2003. The accumulated total in Mars orbit is about two and a half times larger than that aboard the Space Station. Averaged over this time period, about 10 percent of the dose equivalent at Mars is due to solar particles, although a 30 percent contribution from solar particles was seen in July 2002, when the sun was particularly active.

odyssey-radiation.jpg (72744 bytes)

For more information on Mars Odyssey visit  http://marsprogram.jpl.nasa.gov/odyssey/

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Copyright ©2004 Colleen Gino

Images and content courtesy JPL and NASA.