Wild 2 was thought to be a comet
until now. But after NASA’s researchers analyzed some samples of its rock dust,
they realized Wild 2 might not be an ordinary comet after all. It might not be
a comet at all!
According to the United States’
space agency’s recent announcement, it seems that scientists are forced to
alter the way they think about comets and asteroids, these space objects that
are always in a hurry to streak through our solar system.
So, when NASA’s Stardust
spacecraft brought on Earth Wild 2’s rock dust, everybody thought they would be
analyzing a comet’s dust. But the research proved that Wild 2 was much more like
an asteroid than scientists had ever expected!
According to the traditional definition,
comets are celestial bodies made of rock, dust and ice. They are formed
somewhere in the solar system and they have characteristic tails of dust and
gas streams. According to the long-standing theory, comets are a kind of frozen
time capsule of material from when the solar system formed about 4-1/2 billion
years ago.
But despite the fact that it
looks like a comet, Wild 2’s composition is different of that of a comet. A lot
of the material scientists detected in its dust seems to have formed very close
to the sun in the early solar system and was later transported to the outer
solar system. On the other hand, the dust resembles a lot the material from the
chondritic meteorites from asteroids in the asteroid belt between Jupiter and
Mars. Asteroids and comets are not the same thing, as asteroids are fragments of
ancient space rubble, made of metal and rock; asteroids usually orbit the sun
in that belt.
"Overall, this comet, Wild
2, is looking a lot more asteroid-like than we had expected," said Hope
Ishii of the U.S.
government's Lawrence Livermore National Laboratory, one of the researchers
involved in this study.
"The material found in
primitive objects just wasn't there in the samples," another of the
researchers, John Bradley of the Lawrence Livermore National Laboratory, stated.
"I think this is science in action. It's really exciting because it's just
not what we expected."
