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Missions to Pluto, Europa Canceled


NASA's on-again, off-again mission to Pluto appears to be off, at least for now. And a JPL mission to Jupiter's watery moon Europa--considered the most likely spot for extraterrestrial life--also has been canceled for budget reasons.

Top NASA officials said Friday it was highly unlikely that a mission to Pluto would launch by 2006--the final date set by scientists to be able to reach the planet in time to study its atmosphere before it becomes inaccessible for a century. The Europa mission was canceled after its projected cost more than doubled.

Though a darling of schoolchildren and a long-elusive target of scientists, a Pluto expedition is not favored by the White House. For the second year in a row, the administration budget has included no money to explore the distant world.

Last year, Congress added $30 million to NASA's budget to develop plans for a Pluto mission after a flood of letters and calls from distraught children and concerned citizens. But this year, scientists at the Applied Physics Laboratory at Johns Hopkins University in Baltimore were refused the $122 million they say is necessary to continue developing a $500-million mission.

Even if Congress again restores funding at the last minute, the unmanned mission faces two significant hurdles, said Chris Scolese, NASA's deputy associate administrator for space science.

It has yet to be proved, he said, that the distant mission is feasible. In addition, the use of plutonium in the spacecraft, to power its instruments, remains controversial.

In other spacecraft, including Cassini, which is bound for Saturn, it has generally taken about eight years to receive permission to use plutonium, Scolese said. Opponents of using the radioactive material fear contamination from a spacecraft accidentally returning to Earth; NASA says the plutonium is well shielded, minimizing any risk.

Finally, the mission is scheduled to leave Earth aboard a new rocket--either a Boeing Delta IV or a Lockheed Martin Atlas V. Both rockets have yet to take their maiden voyage; NASA officials would want the rockets to be well proved before using them to launch spacecraft.

Life on Europa Thought Possible

The mission to Europa was canceled after its $650-million budget swelled to $1.4 billion. The mission could compete for funding in the new NASA budget if its cost is trimmed back to $650 million. But scientists think it is unlikely that they could conduct an effective mission to probe the icy moon's subsurface oceans for traces of life for less than $1 billion.

Most of the staff working on the Europa mission at the Jet Propulsion Laboratory--80 to 90 people--are continuing to work on a new generation of faster, smaller radiation-hardened electronics that were part of the project and will now be used to improve future missions. Others have been redeployed to work on a Mars rover project. Lab officials said the move resulted in no layoffs.

Planetary scientists and those in favor of exploration are angered by NASA's move. Reaching Pluto and Europa is among the top priorities for solar system exploration. Pluto was considered especially urgent because it is entering a distant, colder part of its elliptical orbit. This means the atmosphere will freeze completely and could be unavailable for study for roughly 100 years.

Lou Friedman, executive director of the Planetary Society, called the decisions shortsighted and called them the equivalent of "recalling the fleet."

Colleen Hartman, who directs solar system exploration for NASA, said it may still be possible to reach Pluto and Europa in the near future as technologies such as nuclear propulsion evolve. "We're doing things now that seemed impossible five years ago," she said.

Hartman was also awaiting a survey, done once a decade by the National Academy of Sciences and due out in August, that will set priorities among scientific goals for planetary exploration. A strong push to get to Pluto or Europa from the respected organization could resurrect funding for the projects.

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