SSS 2008-01-25（在线收听）

This is Scientific Americans' 60-Second Science, I'm Chelsea Wald. Got a minute?

Remember the good old days when we understood our solar system? Then we found out Pluto wasn't a planet. And now a new study puts comets in question. The data come from NASA's Stardust Mission. That's the one that scooped up particles from comet WILD TWO and returned to earth two years ago. The conventional wisdom is that comets originated in the outer solar system, then the sun or a planet nudged them into weird orbits. Well the study in the journal Science contradicts that wisdom. It turns out that the particles from WILD TWO look like they belong not to a comet but to an asteroid from the inner solar system. In fact, Stardust didn't capture any of the presolar system stuff that comet should be made of. This means that the distinction between asteroids and comets may be surprisingly blurry. Some comets might have migrated out from the inner solar system or there could be lots of inner solar system stuff in the outer solar system. Either way, it's time to start rewriting those astronomy text books again.

Thanks for the minute, for Scientific Americans' 60-Second Science, I'm Chelsea Wald.