Scientists dispatched the Stardust science probe to get a look at material they thought had formed in the far outskirts of the solar system. Instead, they uncovered proof that the same type of particles forged near the sun ended up in a frozen comet’s body.
University of Wisconsin’s Noriko Kita and colleagues used a unique ion microscope to probe the tiny grains, the largest of which is about one-thousandth of an inch across. They found oxygen isotope ratios that closely resemble materials in asteroids, meteorites and even the sun itself.