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The news, though not unexpected, still comes as a shock to the project team at the Jet Propulsion Laboratory, which has worked on mission plans for a decade. Rumors about the mission's shaky status first surfaced in July, when Weiler's office began looking for savings to offset the increased cost of NASA's Mars-exploration plans. Efforts that were running over budget got extra scrutiny, and the Pluto mission's projected cost has risen sharply over its $400 million estimate. According to Weiler, "Pluto is greatly deferred, not canceled," and the effort will now focus on reaching the planet by 2020. As envisioned, the PKE spacecraft would have left Earth in late 2004 and arrived at the distant planet eight years later. Money scavenged from the Pluto project will be applied toward developing a Europa orbiter, now due for launch in 2006.
PKE isn't the only casualty of NASA's internal cost-cutting. Weiler has also decided to shut down the Extreme Ultraviolet Explorer satellite at year's end. Launched in 1992, EUVE continues to study high-energy cosmic sources, though the primary mission's surveys and single-target work were completed years ago. Disappointed astronomers had hoped to receive EUVE data until the spacecraft reentered Earth's atmosphere sometime in 2002.
U N I V E R S E
T O D A Y
Space Exploration News From Around the Internet, Updated Every Weekday.
July 28, 2000 - Issue #281
It looks like NASA is seriously considering cancelling the Pluto Express mission, which was supposed to launch 2004. Pluto's the only planet in the solar system that hasn't been observed close up, and I really think it would be a shame to cancel this mission. The Planetary Society is organizing its members and friends to protest this decision, so if you want to get involved, visit their site, and take part:
February 3, 1999
The International Astronomical Union in Paris now says it has no plans to demote Pluto.
University of North Carolina-Chapel Hill
Chapel Hill, NC 27599-6210
Jan. 26, 1999
CHAPEL HILL -- Even as some astronomers debate whether Pluto should be called a planet, Pluto is approaching a special occasion.
Most people think of Pluto as the most distant planet in our solar system. However, for the past 20 years, Neptune has served in that role. Because Pluto has a more elliptical orbit compared to the other planets, it is positioned closer to the sun than Neptune for about 20 years out of its 248-year orbital period.
Pluto moved closer to the sun than Neptune in February 1979 and was closest to the sun (perihelion) in September 1989. Now headed back out, Pluto reclaims its title as the most distant planet in the solar system on Feb. 9, 1999.
The next time Pluto's orbit leads it closer to the sun than Neptune, in 228 years, the event may not seem as special. It will still occur, but if Pluto has been reclassified as a Kuiper Belt Object, then many people may not pay attention.
Pluto is definitely an odd planet. The other planets tend to fall into two groups: the small, rocky, dense, terrestrial planets of Mercury, Venus, Earth and Mars, and the giant, Jovian planets of Jupiter, Saturn, Uranus and Neptune. Pluto is smaller and significantly less dense than the terrestrial planets. In terms of size and density, it often is compared to some large- and medium-sized satellites of the Jovian planets.
However, some astronomers believe Pluto represents a recently discovered group of objects found in orbit around the sun near and beyond Plutošs own orbit. These objects are called Kuiper Belt Objects (KBO) in honor of the astronomer who predicted their existence. To date, Pluto is considerably larger than any of the discovered KBOs.
Although Pluto, especially at this place in its orbit, is close compared to the stars, it is extremely faint. Pluto is now about four light hours away while Sirius, the brightest star in the night sky, is about nine light years away. Despite the fact that Pluto is 18,000 times closer to us than Sirius, Pluto appears 1.2 million times fainter than Sirius to an earthly observer.
University of Kansas
January 22, 1999
"There is no plan to 'downgrade' or 'demote' Pluto," says Brian Marsden, head of the International Astronomical Union's Minor Planet Center. "It will stay as a planet."
Sometime early this year, it's likely Pluto will be designated a "transneptunian object" -- but not lose its planetary status, as has lately been rumored.
The designation, new for Pluto, already describes a group of 90 known bodies on the outer fringes of the solar system.
"This is like giving it a social security number," Marsden said. "Humans acquire names soon after birth. Later they get social security numbers. Does having the latter demote them in some way? Of course not."
Controversy has swirled around the pint-sized planet for various reasons, including its smallness and eccentric orbit. But the possibility of its being demoted touched nerves.
Among the miffed was Patricia Fort Johnson, a former resident of Streator, Ill. Pluto's discoverer, Clyde Tombaugh, was born near there.
Tombaugh attended high school in Burdett, Kan., and went to school at the University of Kansas, in Lawrence, so the possible demotion rankled folks in those towns, too. At KU, an observatory is named after Tombaugh.
Johnson recently wrote to Steve Shawl, KU professor of physics and astronomy, about her distress.
"I would be sorely disappointed," she told Shawl, "if Pluto were to be demoted from planet status. Where would be our truth?"
It was Shawl who put her in contact with Marsden, who responded with assurance and the social security analogy.
All this amounts to quite a bit of fuss over an odd little ball. Pluto is only about 1,450 miles across, about the distance between Kansas City and Las Vegas. It's considerably smaller than Earth's moon, which is about 2,150 miles across.
That's only one reason some people don't consider it a planet. Another is that it breaks a trend in the solar system, says Bruce A. Twarog, KU professor of physics and astronomy. While the inner planets, out to Mars, are basically orbiting rocks, the outer ones are gigantic gas balls -- until you get to Pluto, says Twarog.
If you drilled from the surface of Pluto toward its center, you'd be boring through ice the first quarter of the way. It's nothing you'd want to put into a margarita though, being frozen nitrogen, carbon monoxide and methane.
Currently, Shawl says, Pluto has a thin atmosphere. That's only because it's as close to the sun as it ever gets, and the heat is changing some of the ice into gas.
Pluto orbits the sun every 248 years, moving, unlike other planets, in a big ellipse rather than a circle.
For about 20 of those 248 years, it's closer to the sun than Neptune, which is ordinarily the eighth planet out from the sun, Shawl says. In fact, Pluto has been the eighth planet since Jan. 21 ,1979, but becomes the ninth planet again on Feb. 11 of this year -- and the pro-Pluto crowd can breathe a sigh of relief that it will still be a planet on that date.
Despite Pluto's eccentricities, the debate about whether it's a planet is "much ado about nothing," Shawl says.
David Tholen, a KU graduate now at the University of Hawaii, adds, "Debating the dividing line between planet and minor planet, or asteroid, is like debating the dividing line between city and town, river and stream."
"It's nothing that should send anybody out of orbit," Shawl says.