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."