Astronomers See Pluto, Jupiter as Top Missions

A panel of astronomers charged with steering the nation’s exploration of the solar system called on NASA Thursday to resurrect missions to Pluto and Jupiter’s moon Europa--two high-profile projects the space agency canceled earlier this year for budgetary reasons.

The space agency responded to the National Academy of Sciences report immediately, boosting hopes for the once-doomed mission to Pluto--the last unexplored world in our solar system.

“We are already in discussions to see what are the options to reach Pluto by 2020,” said NASA spokesman Don Savage.

The report came as welcome news to Alan Stern, a planetary scientist at the Southwest Research Institute in Boulder, Colo., and the lead scientist on the “New Horizons” mission to study Pluto, its moon Charon and three other objects in the distant Kuiper Belt. Stern has been through so many ups and downs with the mission, he had taken to calling his team “the undead.”

“This is a major relief,” he said. “I’m going to get more sleep now.”

The mission, which was not funded by NASA until Congress stepped in, still requires $120 million in next year’s budget to launch by 2007. That is the last date a Pluto-bound craft could travel the 3 billion miles relatively cheaply by using Jupiter’s gravitational field as a slingshot. It looks as if that money--1% of the NASA budget--could be forthcoming.

“Last year I fought to put $30 million in NASA’s budget to start the Pluto mission,” said Sen. Barbara A. Mikulski, a Democrat from Maryland who heads the Senate subcommittee that oversees the NASA budget. “I intend to restore funding again this year, despite NASA’s failure to include money for Pluto.”

Louis Friedman, executive director for the Pasadena-based Planetary Society, has been lobbying vociferously for the space agency to resume plans to reach Pluto and Europa. A letter-writing campaign led by the society to support the Pluto mission had been derided by some as pushing a project that was popular with the public but of marginal importance to science.

“They can’t say that anymore,” said Friedman. “The public interests and the scientific interests are the same.”

The panel said that the icy “planetesimals” that fill the Kuiper Belt are the most primitive material in our solar system--cosmic fossils that provide a glimpse into our planet’s origins.

The National Aeronautics and Space Administration commissioned the report after a string of mission failures and cost overruns. Agency leaders asked the panel to list the top scientific priorities for exploration and pick a handful of specific missions for the next decade. It was not an easy task.

“It’s like taking kids to a candy store--everything is interesting and delectable. Everyone wants everything at one time. But you have to prioritize if you want to move forward,” said Dimitri A. Papanastassiou, a Jet Propulsion Laboratory cosmochemist who served on the panel.

Though NASA officials are struggling to rein in costs, the report calls for an aggressive approach to space exploration. It suggests planning now for a series of relatively low-cost missions every 18 months and for “flagship” missions every decade such as Viking, Voyager, Galileo and Cassini that approach $1 billion in cost but return vast amounts of scientific data.

“Answers to some of the most profound questions--Are we alone? Where did we come from? What is our destiny?--may be within our grasp,” said the report, written by a team led by Michael J. S. Belton, a veteran planetary scientist who heads Tucson-based Belton Space Exploration Initiatives.

Flagship missions could include a probe to Europa--thought to be a place hospitable to life because of the vast, liquid oceans that exist under its icy crust. An earlier mission to Europa being planned by JPL was canceled after its price tag swelled to $1.4 billion from $650 million. Much of the extra cost was because of efforts to build a spacecraft that could operate in the high-radiation environment around Jupiter.

NASA officials said it would take some time and new ways of organizing the budget before they could begin funding a Europa mission.

“This is all so new,” NASA’s Savage said. “We just have to look at how we can incorporate it all.”

Another expensive mission would be to bring a piece of Mars back to Earth in an effort to understand how the planet evolved and whether it ever contained life.

A Mars sample return mission has been under study at the agency.

The panel said the next decade should include a “smart lander” mission to drill beneath the surface, a network of science stations around the planet that could take heat flow and atmospheric measurements for a full Martian year, and planning for a Mars sample return mission to occur sometime after 2013.

In general, the planetary scientists who would carry out the missions approved of the new report and priorities, said Mark Sykes, an associate astronomer at the Steward Observatory in Arizona and past chair of the American Astronomical Society’s Division for Planetary Sciences. Sykes solicited about 370 scientists to contribute their views to the process.