Well, the folks at NASA are singing praises for their successful capture and return to earth of “comet stuff.” CNN story. The aerogel material they used to capture bits of Comet Wild2 is peppered with dust and debris from the pristine comet, giving scientists fresh interplanetary material to investigate.
Why all the fuss? Well, the only off-planet materials we have had to investigate have been the moon rocks brought back by the Apollo astronauts, solar wind particles brought back by Genesis and the occasional meteorite. For astronomers to get a real clear idea of how the solar system formed and what it is made out of, they need some unsullied primordial samples.
Current theory goes like this. Roughly 5 to 6 billion years ago, a huge cloud of dust and gas slowly condensed by gravitational attraction into the sun, the planets, the planets’ moons, and a bunch of things called planetesimals spread out well past Pluto’s orbit. Asteroids and comets are among those planetesimals, so Comet Wild 2 is one of the bits leftover from the formation of the solar system. In other words, it’s a cosmic fossil.
Astronomers estimate the age of the sun to be about 5 billion years old, and the earth-moon system to be about 4.6 billion years old. Wild 2 could be older, since it took a while for the sun to “light up,” as it were. Wild 2 is also unusual, in that it apparently has not swung past the sun much, if at all, as have more well known comets like Halley. So, Wild-2 is particularly special, as the sun has not vaporized the comet’s outer layers into space.