Wild Ride: Comet Sample May Help Constrain the Early Evolution of the Solar System
The comets that come streaking through Earth's neighborhood are visitors from frigid, distant regions in the outer solar system. The icy, dusty bodies formed there billions of years ago, far from the heat and radiation of the sun, so it was long thought that they comprised unsullied scraps left over from the solar system's formation. But a new analysis of a particle from Comet Wild 2 indicates that the mote formed close to the sun and then migrated outward to be captured by the comet millions of years after the solar system began taking shape. Along with similar investigations of other samples , the new finding reinforces the theory that comets originating in the Kuiper belt, the distant field of icy debris where Pluto orbits and beyond, contain fragments that formed somewhat later than the solar system's primordial grains, and much closer to the sun. [More] ...