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July
23, 2002 8:45 a.m.
Plutonic
Relationship
Let’s
visit the ninth planet.
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here's only one planet in our solar system that hasn't been explored —
and the Bush administration apparently wants to keep it that way.
That's a shame, because Pluto is one of the most interesting objects out
there. Pluto is the smallest planet, the most distant, and the one with the weirdest orbit. It wasn't even discovered until 1930, and even
then its discovery was an accident — astronomer Clyde Tombaugh was
looking for something else. It took until 1978 to discover Pluto's single
moon, Charon; relative to the size of the body it orbits, no satellite
in the solar system is bigger than Charon.
The Hubble Space
Telescope has taken pictures of Pluto (see here
and here),
but they leave much to be desired. Attempts
to map it have produced only frustrating glimpses of a blotchy surface.
There are plenty
of reasons to visit Pluto. For starters, it's the only planet we haven't
explored with a probe, which means that mankind's reconnaissance of the
solar system is incomplete until we reach it. There's much to learn, too.
As a rocky body far from the sun, Pluto will offer clues about the origin
of the solar system. A National Research Council panel recently
endorsed the scientific value of a mission.
But most important
may be what we don't know. "We're always surprised by what we find
when we visit the planets," says Louis Friedman of the Planetary
Society. Previous missions into deep space revealed that Saturn isn't
the only planet with rings, that Neptune experiences fierce atmospheric
storms, and that Europa (one of Jupiter's larger moons) is home to an
ocean of ice. And whose imagination hasn't been ignited by those gorgeous
pictures of far-away worlds?
Despite this, the
Bush administration has removed funding for a Pluto mission in its 2003
budget. The Senate appropriations committee takes up the matter today
— and it should move to restore the money, which would amount to
$122 million next year in preparation for a 2006 launch and a 2015 flyby.
(A good summary of the whole dispute may be read here.)
Time is running short.
A few years ago, Pluto hit its perihelion — it came as close to the
sun as it gets during its 248-year migration, actually passing within
the orbit of Neptune. It is now headed outward, and there's a concern
its atmosphere will freeze and therefore be impossible study, if much
more time passes. What's more, Pluto's tilted axis will move a growing
share of the planet's surface into long-term darkness; about 7 percent
of Pluto currently faces away from the sun, and that figure will grow
to nearly 25 percent within three decades.
Pluto's severely inclined orbit also will take it far off the ecliptic plane, which means that any follow-on study of the Kuiper
Belt will be less fruitful. And if there's a Planet
X out there — a number of astronomers have surmised the existence
of a tenth planet that may be larger and more distant than Pluto —
a delayed Pluto mission provides a poorer chance of locating it.
Politicians usually
aren't good at looking beyond the next election, but here's a chance for
Congress to bequeath the thrill of discovery upon a generation of children
who are only now being born — and with more success than any federal
bill on science education can ever hope to achieve.
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