Pluto mission revived -- barely

Artist's concept of the Pluto Express spacecraft near Pluto and its moon Charon

By Richard Stenger
CNN.com Writer

(CNN) -- NASA announced Wednesday it was reconsidering a mission to Pluto, the only planet that has not been visited by Earth-launched space probes. Just three months ago, the agency had said it was canceling the project.

The proposed Pluto-Kuiper Express would also fly by Pluto's moon Charon and the Kuiper Belt, a ring of icy objects beyond the planets that may hold clues about how the solar system formed.

Citing cost overruns and technical delays, NASA stopped work on the mission in September. Planetary scientists immediately protested the cancellation, saying indispensable science would be lost unless a Pluto probe was launched as scheduled in 2004.

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"It is the last opportunity for the spacecraft to take advantage of a Jupiter gravity assist to give it the boost it needs to reach Pluto in reasonable flight times," Louis Friedman, director of the Planetary Society, said in a statement.

Timing is critical. Pluto, which has a highly elliptical and inclined orbit, is currently heading away from the sun.

"A later launch pushes the arrival date so far in the future that most of Pluto's tenuous atmosphere might freeze out by the time the spacecraft gets there," Friedman said.

But the revived Pluto Express could easily die again. To cut costs, NASA has decided to accept outside bids to develop the project. Unless the agency finds an acceptable proposal by next autumn with a total price under $500 million, it will drop the mission altogether.

"We are not making a commitment to doing a Pluto mission. We are just looking at proposals," NASA Associate Administrator Ed Weiler told reporters Wednesday.

Improved technology might allow a probe to launch later than 2004 and forgo a Jupiter gravity assist. "The arrival time at Pluto would be a key factor, not a launch date," Weiler said.

Bids for the Pluto mission are due in March.

NASA's Jet Propulsion Laboratory will continue with current plans to develop an orbiter slated to visit Europa, an ice-encrusted moon of Jupiter. Scientists speculate that the large satellite contains a warm salty ocean, a favorable condition for the search for life.

But budget and technology constraints could prevent both the Pluto Express and the Europa Orbiter from launching this decade, according to NASA.

NASA unveils new Mars exploration plan
October 26, 2000
Scientists discover large asteroid between Neptune, Pluto
October 24, 2000
Planet lovers campaign to save Pluto Express
July 28, 2000
Pluto may be stripped of planetary status
January 20, 1999

NASA
Pluto-Kuiper Express
The Planetary Society
NASA Jet Propulsion Laboratory
Europa Orbiter

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