GODDARD SPACE FLIGHT CENTER, June 21 -- A team of astrophysicists has produced the most precise measurement to date of a comet's ratio of carbon monoxide to water. As reported in the magazine Nature, the researchers, from the University of Notre Dame, NASA's Goddard Space Flight Center, and Rowan College in New Jersey, determined that the carbon monoxide/water ratio of the comet Hale-Bopp is 12 percent. The group made their observations of the giant comet in 1997-1998 using an infrared spectrometer on NASA's three-meter telescope at the Infrared Telescope Facility at the Mauna Kea Observatory in Hawaii. These observations suggest that the comet Hale-Bopp was likely formed in the region between Jupiter and Neptune some 4 billion years ago. It's fundamentally important to know the amount and source of carbon monoxide, said Notre Dame's Terrence W. Rettig, associate professor of physics and a participant in the observations. These data provide our most comprehensive clues about where and how Hale-Bopp was formed and give us a better understanding of its history. Astronomers have been studying the visible attributes of comets for hundreds of years but until recently, infrared observations were not possible. In the past several years, infrared detectors have become much more efficient, making these observations now possible.