quarta-feira, 26 de dezembro de 2012
That meteorite which blew-up over California last April is one of the rarest ever found
After disintegrating over California in a 4-kiloton explosion, a team of scientists (including NASA researchers from Ames) scrambled to recover the fragments.
They managed to find a paltry 205 grams worth in the form of 77 pieces, but it was enough to conduct an analysis. They located the exact region where the fragments fell by using doppler weather radar — the first time this technique was used for such a purpose.
Based on photographs of the fireball, the object entered into Earth's atmosphere at an unusually low-inclined comet-like orbit that at one point reached the orbit of Mercury. Consequently, it passed closer to the sun than other recovered meteorites. But at the same time, it experienced an unusually short exposure to cosmic rays. The scientists suspect that it circled the sun three times during a single orbit of Jupiter, an important piece of insight into the object's point of origin.
The ensuing study, which was conducted by Peter Brown and colleagues at Western University and Peter Jenniskens of the SETI Institute, reveals that it was a rare carbonaceous chondrite meteorite — a so-called C-class asteroid that likely came from the Eulalia asteroid family. This is a very primitive class of asteroids that are very rarely discovered. Specifically, it's a regolith breccia that originated from near the surface of an ancient asteroid, possibly in the vicinity of Jupiter.
And importantly, the debris contained carbon. It's rocks like these, say the scientists, that contributed to the early organic chemistry on Earth — the same carbon atoms that can be found in biological matter.
Interestingly, NASA plans on sending astronauts to asteroids like these on future missions.
You can read the entire paper at Science.
Publicado por Jorge M. Gonçalves às 9:30 da tarde