It sounds like a recipe for an astronomy-type video game: first launch a rocket equipped with a telescope into a 5-minute suborbital flight. Then when it gets stabilized, turn the controls over to a pair of scientists and let them use a joystick to point the telescope at a bright comet. The result? The first-ever detection of the noble gas argon in a comet -- and a peek into the deep-freeze of the early solar

nebula where the comet formed.

On Monday, S. Alan Stern, a researcher with Texas-based Southwest

Research Institute reported on the analysis of spectroscopic data collected on March 29, 1997, by a rocket-borne extreme ultraviolet (EUV) telescope and spectrometer launched from New Mexico's White Sands Missile Range. When Stern and his team finished reducing their data just recently, they saw the unmistakable signature of argon gas.

Its presence tells a lot. The argon would have been completely driven off if the bulk of the comet's nucleus had ever experienced temperatures of even 30 or 35 deg. Kelvin since its formation at the beginning of the solar system's history. On the other hand, the rocket team found no trace of neon in Hale-Bopp. Neon is driven off at about 20 deg. Kelvin, implying that the nucleus was heated at least to that temperature.

This tight constraint on Hale-Bopp's heating history implies that the comet most likely formed in the cold reaches of the solar system near where Uranus and Neptune are now -- farther out than astronomers had expected.

Stern and his colleagues, including Michael A'Hearn of the University of Maryland and Michel Festou of the Observatoire de Midi-Pyrenees in France, plan to study other comets using the same technique with better instruments. In coming years they hope to check comets Wirtanen, Machholz 1, and Encke for the presence or absence of other gases that should have existed in the early solar system. "This is very exciting to us," Stern said. "When we look at these comets with other flights, we'll be studying emissions of other species that tell us about what conditions might have been like in the early solar system."