Upon meeting the comet, Tempel 1, in early July 2005,
Deep Impact will take a good look around, take a lot of pictures, and then, on
July 4, it will lob a 220-lb. copper ball into the comet’s mouth.
Actually, Henderson explained, the craft won’t “lob”
the impactor so much as it will “get in position to get run over…like a mosquito
on the windshield of a truck.” Because Tempel 1 is truckin’ along at roughly
22,800 mph, the force of impact can be compared to the blast of about five tons
of dynamite or a really sweet fireworks display.
“The impactor will be vaporized instantly,” Henderson
said, but it will leave a mark: a hole about the size of a football
field.
Clue
to the Universe
In this “controlled cratering” experiment, NASA will
search for answers for two types of people: those who gaze at the sky with
wonder, and those who look up with worry.
For the wonderers, NASA will investigate the layers
of debris and dust inside the comet. Just as layers of earth expose information
about our planet’s past, the comet’s layers should reveal information about the
formation of our solar system.
For the worriers, NASA will analyze the data to
better understand the implications of a potential comet-Earth collision.
Although few of us will see the mission’s initial fireworks display, amateur and
professional astronomers plan to combine efforts with telescopes large and small
to offer an earth-based look at the show.
Meanwhile,
images and data from both the flyby spacecraft and
the impactor will be sent back to Earth on NASA’s aging Deep Space Network
(DSN). Using a worldwide network of 70-meter antennas built in the 1950s and
several newer, smaller ones, the resulting images will be analyzed and then disseminated
by NASA and university scientists to offer a first-ever look deep below
a comet’s surface -- seven to 15 stories below.
Life After Impact
Monte Henderson said Deep Impact was
designed in hopes that the flyby spacecraft would survive the
initial “spew of ejecta” (what the comet will cough up at impact)
and a trip through the comet’s tail. With that in mind, scientists
are working on proposals to use the craft for other deep space
missions. A’Hearn said visits to other comets and asteroids would be
the most logical use of Deep Impact’s flyby capabilities after its
encounter with Tempel 1.
“We will be formally proposing the
extended mission to another solar system target,” he said, probably
the comet Hartley 2. A’Hearn added that other astrophysical uses are
also possible, but at press time this was the only one nearing
formal proposal.
Even if the flyby spacecraft does not
survive impact, the project team will at least have felt the
satisfaction of seeing the mission’s primary objective
completed.
While that scenario sounds somewhat
disheartening, A’Hearn would probably recover quickly. After working
throughout the 1980s on several NASA projects that were cancelled
due to budget reasons, watching the impactor literally blow up in
his face is more than he could hope
for.
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