Switching their focus from the farthest galaxies to Earth's nearest neighbor, scientists using the Hubble Space Telescope have confirmed the presence of a mineral on the moon that might someday provide human explorers with life-sustaining oxygen and rocket fuel.
Researchers said yesterday that they had detected ilmenite - a compound of iron, titanium and oxygen - at two Apollo landing sites and another region never visited.
NASA officials said the work lays the scientific foundation for robotic prospecting missions - an orbiter due for launch in 2008 and one or more landers later. All are designed to help NASA plan for manned landings as early as 2018.
James B. Garvin, chief scientist at the NASA Goddard Space Flight Center in Greenbelt, called the mission, carried out during August's full moon, "one of the technically most challenging observations Hubble has ever done."
It was the first use of the 15-year-old orbiting observatory to support the Bush administration's plans to send astronauts back to the moon and eventually to Mars.
The Hubble project's goal, Garvin said, was to "provide near-term information to help us make key decisions" about lunar exploration, such as where to land and whether explorers can eventually expect to be self-sustaining.
But it will also provide scientists with new knowledge of lunar geology and history.
For Hubble scientists hoping for a shuttle mission to service and upgrade the aging telescope - and keep their research alive - the moon observation was a chance to demonstrate Hubble's horsepower.
Mattias Mountain, director of the Space Telescope Science Institute in Baltimore, called the project "a wonderful synergy between science and exploration."
"What NASA is trying to do is understand this balance between science and exploration, and I think maintaining the appropriate balance is going to be the trick," he said.
But the Hubble telescope's success with the lunar observations does not guarantee its future. NASA officials say the observatory's life expectancy in orbit still depends on approval of a servicing mission to replace aging gyroscopes and batteries.
NASA Administrator Michael Griffin has said he will not schedule a Hubble servicing mission until at least two shuttle flights have returned safely.
The shuttle Discovery returned safely in August on the first flight since the Columbia disaster in 2003. But falling debris during its launch - the same problem that damaged Columbia and doomed its crew - postponed the next flight until at least May or June.
"Hubble is working great right now, and ... we are doing everything we can to keep it operating as long [and] productively as possible," said Jennifer Wiseman, a Hubble scientist at NASA headquarters.
"I don't think that these [lunar] observations will have any impact, one way or the other, on the future of Hubble," she added.
But they do illustrate the telescope's versatility. The idea of using the Hubble for lunar mineralogy first surfaced in 1991, a year after its launch.
Garvin said the telescope's capacity to gather ultraviolet light is impossible to duplicate beneath Earth's atmosphere. It offered a unique opportunity to use reflected light to map minerals on the moon's surface and learn something about its natural history.
NASA turned down Garvin's idea repeatedly over the years. But he resurrected it in 2004, when then-NASA Administrator Sean O'Keefe challenged scientists to find new ways to use existing data and hardware to support the manned exploration initiative.
With scientists and engineers from Goddard, the Space Telescope Science Institute and academia, Garvin submitted the proposal again. This time it survived scientific scrutiny and an independent review to assure it would not threaten the Hubble's health and safety.
The problem: The space telescope was never designed to observe the moon. Its usual targets include the most distant galaxies in the universe, billions of light years away, as well as stars and planets that appear to move very little as they're being observed.
By comparison, Wiseman said, the moon "moves very quickly across the sky as it orbits the Earth. When you try to observe the moon with Hubble, what happens is, you get smearing of the images."
Garvin and his team had to invent new command programs and send them up to the Hubble so it would track the moon as it moved to keep its images sharp and on target.
Garvin likened the job to a blind quarterback trying to aim passes at receivers by predicting their movements - and doing it 60 times in a row with an accuracy of a quarter-inch.
Engineers also had to be sure that light from a brilliant full moon would not damage the telescope's sensitive instruments.
To their amazement, it all worked. Hubble made 60 exposures, snapped over three days during 12 orbits of the Earth.
"This is, in some sense, the miracle on the moon," Garvin said.
Hubble planners targeted the landing sites of Apollo 15 at Hadley Rille in 1971 and Apollo 17 at Taurus-Littrow in 1972.