Stand back, humanoid! Here comes the next installment of the Codex Futurius project, this blog’s never-ending quest to explore the ineffable scientific ideas raised by science fiction. This question on killer asteroids goes to Kevin Marvel, head of the American Astronomical Society. Thanks to Dr. Marvel for the scary info and to Jennifer Ouellette, the director the NAS’ Science and Entertainment Exchange (SEEx) program, for connecting us with him.
Question: How big an asteroid would be needed to completely destroy a planet?
That’s easy. It would have to be really, really big or moving very, very fast (or both for a real whopper of an impact), but there are some subtleties that are worth explaining.
First off, let’s admit that we’re really concerned with how big an asteroid would destroy planet Earth, especially life on Earth. I’m a bit more worried about my home planet than Mars, Jupiter, or even Pluto and even more worried about all the life we see around us (not to mention ourselves!). Earth is far more important from the human perspective, so let’s tackle that question.
Frighteningly, many large objects have hit Earth. Real whoppers. That’s a bit scary to think about. The good news is that the Earth is still here, so apparently large impacts of the planet-destruction kind rarely happen. We do know that smaller impacts have happened, such as the meteorite that hit the high Arizona desert just east of Flagstaff, at the site known as Meteor Crater. If we could count the impacts, we could gauge how frequently and when the impacts took place.
Okay, if you’re not caught up on your BSG, stop reading now! I’ll pause for a moment in case your eyes are like mine and tend to skip ahead for a few words anyway…. So, for those of you who have seen the mid season finale, there is a 
