TAOS, NEW MEXICO The chance that a derelict rocket stage may hit the Moon has stirred up hopes of gathering valuable lunar science data.

In early September, an object was discovered slipping through space. Later tagged J002E3, the mystery flotsam is speculated to be a relic of space programs past: A Saturn IVB upper stage from the Apollo 12 mission that flew in November 1969. After its use, the rocket stage was cast off.

But theres a slight catch.

Starting with the second landing expedition on the Moon, Apollo Lunar Surface Experiment Packages (ALSEPs) were deployed by astronauts. Spread out on the Moons surface, the equipment gathered important science information, from sensing the magnetic field at the lunar surface to probing subsurface materials.

These nuclear-powered ALSEPs also included a passive seismometer.

The Passive Seismic Experiment used four extremely sensitive seismometers to measure lunar surface vibrations, free oscillations, and tidal variations in surface tilt. The electronics of the experiment were housed in the ALSEP central station. A thermal shroud isolated the sensor as well as a patch of ground several feet in diameter from temperature extremes of the lunar day and night.

These seismometers were built to detect the natural rumbles from "moonquakes." They also registered the deliberate crashing into the Moon of human-made objects in the Apollo era. Those crashes involved several spent lunar module ascent stages -- the top part of the lunar lander that whisked astronauts off the Moon to the awaiting Apollo Command Service Module -- as well as a number of Saturn IVB stages purposely sent careening into the Moon.

Now, heres the catch: In a money-saving decision, the ALSEP packages were "gracefully" shut off in late September 1977. The question is, can they be reactivated?

"If we find that its possible to turn the ALSEPs on in anticipation of a hit by an upper stage of a Saturn V, then I think there would be a tremendous scientific return," said Apollo 17 moonwalker, Harrison Schmitt. The former astronaut and professional geologist was the last man to step onto the Moon in December 1972.

Schmitt was in attendance at The Moon Beyond 2002: Next Steps in Lunar Science and Exploration held here Sept. 12-14.

NASA should look into the possibility of turning the Apollo 12, 14, 15, and 16 ALSEP hardware back on, depending on how long they could be left on for a reasonable cost, Schmitt said. "The Apollo 17 seismometer probably wouldnt be of any use," he said. "It had a mistake in its design and wasnt really built for that kind of information anyway."

But bringing back to life an ALSEP network on the Moon would be a scientific bonus.

"You always have the possibility of getting additional sizable impacts that can add to the general understanding -- much more than we have now -- about the interior structure of the Moon," Schmitt said.

In the past, by using Saturn Vs upper stages as sources of energy, Schmitt said, the ALSEP seismometer network yielded a primary source of data about the crust and mantle of the Moon in certain regions.

Schmitt said that he and other lunar scientists plan to look into the ALSEP reactivation matter, given the knowledge that the rocket stage will indeed strike the Moon at some point.