Thread: Which rock killed the dinosaurs?

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Light Years

Which rock killed the dinosaurs?

The plot thickens

September 20, 2011, 10:20 am ET (CNN) — A 65-million-year-old murder mystery just got a bit more mysterious.

Which “family” of asteroids killed earth’s dinosaurs? New data from NASA’s orbiting Wide-field Infrared Survey Explorer (WISE) throws doubt on a 2007 theory that blamed the death of the dinosaurs on fragments from an asteroid family called Baptistina, located between Mars and Jupiter. Baptistina was a huge asteroid which crashed into another space rock millions of years ago, sending mountain-sized pieces flying in various directions.

Scientists had theorized one of those Baptistina fragments slammed into the Gulf of Mexico, triggering the end of Earth’s reptile dynasty. The earlier Baptistina estimates were off, says Lindley Johnson, program executive for the Near Earth Object (NEO) Observation Program at NASA Headquarters in Washington.

“With infrared light, WISE was able to get a more accurate estimate.”

Infrared light is electromagnetic radiation which humans sense as heat.

Reconstructing what really happened so many millions of years ago sounds very much like a script from a detective show. Baptistina broke up into chunks about 15 million years before the dino-killing event, according to WISE data — which doesn’t fit scientists’ timeline. In this crime of epoch proportions, that gives Baptistina a pretty good alibi.

Baptistina asteroids apparently were nowhere near the scene of the crime because it likely would have taken millions of years longer for them to drift into regions of space called resonances.

Resonances have gravitational forces created by Saturn and Jupiter which can shoot asteroids toward Earth — sort of like a pinball machine.

“It doesn’t completely rule it out as the source of the dino-killing culprit,” says Amy Mainzer, who co-authored the WISE study. “But it does give theorists something new to think about.”

What damaged the Baptistina theory? Mainzer’s team measured the size and amount of sunlight reflected from 120,000 asteroids, including 1,056 members of the Baptistina Family. From that data, they calculated how much time it took these asteroids to reach their current locations.

When Mainzer talks about the project, the conversation is sprinkled with vocabulary you might hear in a gangster flick or an episode of “Law & Order.” There are no “major suspects”* in the case, she says — now that Baptistina is in the clear. She plans to create “family trees,” for thousands of asteroids — conjuring up images of FBI bulletin boards with photos of Mafia crime bosses connected by pieces of string.

“The first thing we want to do is look at the whole asteroid belt and really kind of go back to Square One and say, ‘OK, what are the major families that we know about in the asteroid belt and which are the most likely culprits?’” she says.

Ironically, Mainzer’s position in the project is labeled “principal investigator.” The asteroids in our solar system’s main asteroid belt range in size from about 0.6 miles wide to 583 miles across. In fact, about once a year a car-sized asteroid strays toward earth and burns up while entering the earth’s atmosphere, according to NASA.gov.

By the way, astronomers recently surprised Mainzer by naming an asteroid after her called “234750 Amymainzer.”

“We did indeed observe it with WISE,” she says. “It is a bit funny to have your namesake be a seven kilometer chunk of charcoal-dark rock!”

Fortunately, she jokes, asteroid Amymainzer poses no hazard to the Earth or its inhabitants.

What’s next? Just like any good police investigation, you need to establish a credible timeline. “We’ve got to go back in time as it were to reconstruct what happened using the huge amount of new information we now have thanks to WISE,” says Mainzer. “That’s going to help point us in the right direction, I hope.”

Posted by: CNN's Thom Patterson

758 Comments

1. Chris
September 20th, 2011 10:54 am ET
I thought the small theropods survived and evolved into birds….

2. Miron Huhulea
September 20th, 2011 10:56 am ET
“She plan’s to create”? That’s the most creative use of the possessive case I’ve ever seen. Unfortunately, no major news organization — CNN, BBC, WSJ — is free from these kinds of egregious grammatical errors anymore.

3. Josh
September 20th, 2011 11:01 am ET
The crack rock!

4. Oldbear
September 20th, 2011 11:02 am ET
Interesting, but how does this help identify potential problems for earth in the near future-1-10 years?

(snip)

From CNN.com