What’s Going on with the Dinosaur-Killing Asteroid?

Introduction

A NASA press release spawned many, many headlines this week in pretty much all newspapers and online news sites, both major and minor, with variations on the theme of, “The origin of dino-killing rock is back to being a mystery.” If somehow you managed to miss the news, I invite you to read the BBC version, though you could also read the original NASA press release.

So, what’s going on here? Is this another case of the media blowing headlines out their collective … well, mouths? Or is there something to this where we’re no longer sure what may have ended the dinosaurs?

2007 Paper

As may have been obvious from the way I worded the question, the answer is very much the former: Headlines are meant to grab you and to be sensationalist so you’ll read the story. Stretching the story or even missing the point are generally irrelevant.

The actual story goes this way: In 2007, Bill Bottke and two co-authors had a paper in the journal Nature entitled, “An asteroid breakup 160 Myr ago as the probable source of the K/T impactor.” The article was actually much more than that, and an extension from their conclusions was that based upon their modeling, the timing for an asteroid breakup would work dynamically for spawning the asteroid that killed the dinosaurs.

Yes, the asteroid theory for the destruction of the dinosaurs is still valid, it is still by far the best one out there and the one that fits the most data the best. So let’s get that sensationalist headline grabber out of the way.

Again, the crux of the Bottke et al. article was that they dynamically modeled an asteroid family (a group of asteroids that travel together and likely formed from an original, larger asteroid, that broke up). This particular family is called the Baptistina family. Based on an assumed brightness for the asteroids, they can estimate their mass and subsequent sizes. Based on how spread out the family is, they can model when it broke up, and the mass also factors into this calculations. Based on all these, their results show that the Baptistina family formation event could have spawned the asteroid that we pretty much “know” resulted in the destruction of the dinosaurs.

Edited to Add: I have a follow-up post from the author of the 2007 paper, Bill Bottke.

2011 Paper

This brings us to the press release and subsequent hubbub this week. The new paper talks about a lot of things, but what’s most applicable is that they have a better measurement of the brightness of these asteroids, and it’s around a factor of 5 times brighter than what Bottke et al. assumed (based on some of this paper’s teams own assumptions, though it’s likely a more accurate result).

The result is that there is much less mass and smaller sizes of the asteroids in the Baptistina family. Meaning that it disperses more quickly (so would have broken up more recently). And finally meaning that the likelihood that it was the source of the asteroid that led to the death of the dinosaurs is much smaller.

To Repeat

No, this does not mean that an asteroid didn’t wipe them out. It does not mean it was a comet. It does not mean it was aliens. It does not mean it was volcanoes. It does not mean it was the Earth growing in size so the dinosaurs got crushed under their own weight. It does not mean it was [insert: whatever the person you read before coming here invented].

It means that the likelihood that the impactor is from the formation event of this family of asteroids is now significantly smaller.

Final Thoughts

Really, that’s about it. But “Higher reflectivity of asteroid family means scientists less certain of the source of the asteroid that likely killed the dinosaurs” does not a good headline make. Oh well.

Edited to Add: I have a follow-up post from the author of the 2007 paper, Bill Bottke.

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