Nasa gladly loses a spacecraft
By Tim Radford
For thousands of years comets have been a
mystery to man. They travel across the sky
very fast and have a bright ‘tail’ of
burning gas. The comet Tempel 1 has an
orbit far outside
the orbit of the furthest
planet in our solar system, Pluto. It has
been there for 4.6 billion years, 133
million kilometres from Earth. Last week
a little American spacecraft crashed into
Tempel 1. The spacecraft had a camera
and it took a photograph of the comet
every minute before it finally crashed into
its surface.
The space mission to Tempel 1 cost $335
million and was called Deep Impact. The
spacecraft was travelling at 37,000
kilometres per
hour when it hit the comet
and the crash completely destroyed the
spacecraft. But before it hit the comet, the
spacecraft took some amazing
photographs. The last one was a close-up
picture which the spacecraft took just 3
seconds before it crashed into the comet.
"Right now we have lost one spacecraft,"
said a delighted NASA engineer. Deep
Impact was like an American
Independence Day fireworks display. It
took many years to plan and ended in an
enormous explosion.
The spacecraft which crashed into the
comet was made of copper and was the
size of a washing machine. It was dropped
from a mothership
into the path of the
comet and the mothership then
photographed the cloud of ice, dust and
organic chemicals that rose from the
surface of the comet after the crash.
The crash completely destroyed the
spacecraft but nothing really happened to
the comet: experts believe that the crash
slowed the comet down by no more than
1/10,000
th
of a millimetre a second. The
aim of the mission
was to study for the
first time the interior of a comet.
The mothership was 480km from the
explosion and observed the crash and the
explosion with instruments for 800
seconds. Seven satellites, including the
Hubble space telescope, watched the
moment of drama, and over the next day
and night about 50
telescopes on Earth
were watching the distant comet.
The first people to produce pictures in
Britain were pupils from King's school,
Canterbury. They used information from
the 2m Faulkes telescope in Hawaii, a
telescope used by schools. Scientists from
the US and around the world were
delighted. For the first time, they had clear
and close-up pictures of a comet.
Comets like Halley’s Comet which visit
the Earth frequently are not so interesting
for scientists. But comets like Tempel 1
are so distant
that they could hold the
secrets of the planets, the Earth's oceans
and even of the original organic chemistry
from which life developed. "If you are
thinking of comets as possible sources of
organic material, then you are looking for
the organic elements carbon, hydrogen,
oxygen,
nitrogen," said John Zarnecki of
the Open University.
For Andrew Coates of the Mullard space
science laboratory of University College
London, Deep Impact was a fantastic
success. "You have the comet getting
bigger and bigger in the field of view, the
level of detail on the comet getting better
and better," he said. "We know that
comets produce jets. What we have now is
the first
artificial jet from a comet," he
added. "The fact that there are craters tells
us the surface must be solid in some way.
This is going to be really exciting."
The Guardian Weekly 15/07/2005, page 19
©
Macmillan Publishers Ltd 2005
Taken from the
Magazine
section in
www.onestopenglish.com
