An artist's concept of Mars Odyssey with its boom deployed. Photo: NASA/JPL

A 20-foot boom was deployed on NASA's 2001 Mars Odyssey Tuesday so the space probe can accurately map the composition of the Red Planet and continue the search for water.

The boom -- with the gamma ray spectrometer sensor head instrument on its end -- took less than 10 minutes to extend, said Bob Berry, the Odyssey program manager for builder Lockheed Martin

"It's the last major configuration change to the spacecraft in orbit around Mars," Berry said in an interview Tuesday evening. "It deployed just as planned."

The gamma sensor head is part of the gamma ray spectrometer suite. It sits at the end of the boom to minimize interference from any gamma rays coming from the spacecraft itself. The two other gamma ray spectrometer instruments, the neutron spectrometer and the high-energy neutron detector, are mounted on the main spacecraft structure.

During the past few months, while the boom was in the stowed position, the instrument suite has provided significant information about the hydrogen abundance on Mars. This allowed scientists to conclude there are large quantities of water ice just below the surface.

"Deploying the boom enhances the sensitivity and accuracy of the gamma ray spectrometer instrument and will improve the accuracy of the hydrogen measurements," said Dr. William Boynton, principal investigator for Odyssey's gamma ray spectrometer suite at the University of Arizona, Tucson.

Now the instrument is sufficiently away from the satellite's main body that obscures the observations of other elements, it can begin measuring such things as iron, aluminum, potassium, chlorine, thorium and uranium.

"The 2001 Mars Odyssey GRS instruments have already provided a great deal of information that will answer many questions. The mission is just beginning; we are optimistic the remainder of the science mission will provide significant information that will help us understand 'where the water went,' as well as significantly increasing our understanding of the origin, geology and climate history of Mars," Boynton said.

"Today's deployment is a continuation of the excellent performance of this flight team. They have done an outstanding job," said Roger Gibbs, Odyssey's project manager at JPL. "I look forward to many exciting discoveries to come as we continue our mission."

Berry said now that all of Odyssey's appendages are deployed, the craft can settle into the routine mapping of Mars for the next several Earth years.