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Scott Mair
 My American friends like to celebrate their
independence day with a bang. I think they may be overdoing
it this year. On July 4th at 1:52 am EDT (10:52 pm, July 3
for us in Victoria) NASA's Deep Impact spacecraft will fire
a 1 metre wide, 113 kilogram copper alloy bullet at Comet
Temple 1.
What did Temple 1 ever do to deserve this? Just good luck.
Temple 1 is a short period comet, circling the sun every 5.5
years pretty much on the same plane as the Earths's orbit
around the sun so it's pretty easy to get to, as far as
comets go.
It seems like a lot of trouble to go through: send a 410
million dollar spacecraft 133 million kilometers in less
than six months to make a hole 2 to 14 stories deep into a
dirty snowball traveling at 37,000 km/hr (at those speeds
you could travel from Victoria to Toronto in 6 minutes).
With our luck the impact will change the comets trajectory
and it will crash into the earth. Not to worry, the impact
will be about the same as a mosquito crashing into a 747.
Why bother? What we know of comets today comes from their
surfaces, coal black, carbon rich crusts created from
multiple trips around the sun. But, in their interiors is
the stuff of the burgeoning solar system. Comets retain,
largely unchanged, the original composition of the early
solar system. Blasting our way beneath the crust will help
us understand the formation of our solar system.
We also know that all of the planets have undergone
bombardment from asteroids and comets (remember Comet
Shoemaker-Levy 9's encounter with Jupiter, July, 1994).
Being rich in water and organic molecules comets may have
helped to seed the building blocks of life on the young
Earth. Deep Impact will help shed light on these mysteries.
I know I'll be watching. Even though it won't be very dark
in Victoria at the time of impact, I'll have my telescope
pointed above and a little east of Spica, the brightest star
in Virgo (which is just east of Jupiter, the brightest
'star' in the sky). Ordinarily, Temple 1 is only a magnitude
10 object (that's dim, you'll need a telescope to see it)
but, if the impact goes as planned it may get bright enough
to see with the naked eye (magnitude 6). Regardless, I'll be
checking out the Deep Impact web site (www.nasa.gov/deepimpact
or
deepimpact.jpl.nasa.gov) in the following days to see
the pictures. the Deep Impact orbiter will have a
front row seat, only 700 km away.
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