NASA's WISE raises doubt about asteroid family believed responsible for dinosaur extinction

While scientists are confident a large asteroid crashed into Earth, leading to the extinction of dinosaurs, they do not know exactly where the asteroid came from or how it made its way to our planet.

By NASA Headquarters, Washington, D.C. — Published: September 20, 2011

This artist's concept shows a broken-up asteroid. Credit: NASA/JPL-Caltech

Observations from NASA's Wide-field Infrared Survey Explorer (WISE) mission indicate that the family of asteroids some believed was responsible for the demise of the dinosaurs is not likely the culprit, keeping the case open on one of Earth's greatest mysteries.

While scientists are confident a large asteroid crashed into Earth approximately 65 million years ago, leading to the extinction of dinosaurs and some other life-forms on our planet, they do not know exactly where the asteroid came from or how it made its way to our planet. A 2007 study using visible-light data from ground-based telescopes first suggested the remnant of a huge asteroid, known as Baptistina, as a possible suspect.

According to that theory, Baptistina crashed into another asteroid in the main belt between Mars and Jupiter about 160 million years ago. The collision sent shattered pieces as big as mountains flying. One of those pieces was believed to have impacted Earth, causing the dinosaurs' extinction.

Since this scenario was first proposed, evidence developed that the Baptistina family of asteroids was not the responsible party. With the new infrared observations from WISE, astronomers say Baptistina may finally be ruled out.

"As a result of the WISE science team's investigation, the demise of the dinosaurs remains in the cold case files," said Lindley Johnson from NASA Headquarters in Washington, D.C. "The original calculations with visible light estimated the size and reflectivity of the Baptistina family members, leading to estimates of their age, but we now know those estimates were off. With infrared light, WISE was able to get a more accurate estimate, which throws the timing of the Baptistina theory into question."

WISE surveyed the entire celestial sky twice in infrared light from January 2010 to February 2011. The asteroid-hunting portion of the mission, called NEOWISE, used the data to catalog more than 157,000 asteroids in the main belt and discovered more than 33,000 new ones.

Visible light reflects off an asteroid. Without knowing how reflective the surface of the asteroid is, it's hard to accurately establish size. Infrared observations allow a more accurate size estimate. They detect infrared light coming from the asteroid itself, which is related to the body's temperature and size. Once the size is known, the object's reflectivity can be re-calculated by combining infrared with visible-light data.

The NEOWISE team measured the reflectivity and the size of about 120,000 asteroids in the main belt, including 1,056 members of the Baptistina family. The scientists calculated the original parent Baptistina asteroid actually broke up closer to 80 million years ago, half as long as originally proposed.

This calculation was possible because the size and reflectivity of the asteroid family members indicate how much time would have been required to reach their current locations — larger asteroids would not disperse in their orbits as fast as smaller ones. The results revealed a chunk of the original Baptistina asteroid needed to hit Earth in less time than previously believed, in just about 15 million years, to cause the extinction of the dinosaurs.

"This doesn't give the remnants from the collision very much time to move into a resonance spot, and get flung down to Earth 65 million years ago," said Amy Mainzer from NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "This process is thought to normally take many tens of millions of years." Resonances are areas in the main belt where gravity nudges from Jupiter and Saturn can act like a pinball machine to fling asteroids out of the main belt and into the region near Earth.

The asteroid family that produced the dinosaur-killing asteroid remains at large. Evidence that a 6-mile (10 kilometers) asteroid impacted Earth 65 million years ago includes a huge, crater-shaped structure in the Gulf of Mexico and rare minerals in the fossil record, which are common in meteorites but seldom found in Earth's crust. In addition to the Baptistina results, the NEOWISE study shows various main belt asteroid families have similar reflective properties. The team hopes to use NEOWISE data to disentangle families that overlap and trace their histories.

"We are working on creating an asteroid family tree of sorts," said Joseph Masiero, also of JPL. "We are starting to refine our picture of how the asteroids in the main belt smashed together and mixed up."

User Comments

Be the first to leave your comment below!

Only registered members of Astronomy.com are allowed to comment on this article. Registration is FREE and only takes a couple minutes.

Register Today!

RICHARD M EISLER from VIRGINIA said:

Maybe its time for another asteroid to hit Earth to cause a homo sapiens extinction. That would be a faster way to get some intelligent creatures on this planet rather than have us produce a gradual extinction

Submitted: 9/25/2011 8:17:53 PM (CST)

WESLEY WOZNIAK from WASHINGTON said:

This suggests that solar system temp. plays a big roll as to growing or braking apart of smaller planetary bodies. Electro static charge build up being a big factor as well. Is there a graph showing the ratio between molten body impact accretion growth, vs. cooler body demolition at given impact sizes and velocities? Are there impacts on other inner solar system planets that happened around that same time period? Could debris form the impact 65 million years ago end up striking Mars or Venus? Have there been any meteorites recovered, that where once part of the Earth that reached escape velocity, only to returned many years later? Is there a solar system model that shows these asteroid fields as planetoids with stable orbits? Or where these always considered dangerous transients that, after destruction, got swept into stable orbits?

Submitted: 9/20/2011 7:09:14 PM (CST)

BILL SIMPSON from LOUISIANA said:

I don't believe a word of it. It came from space. It made its' way here because it was flying around out there and happened to hit Earth. Kind of like, if you go to billions of baseball games, you could get hit by a baseball. No doubt the word 'dinosaurs' got a lot more people to read the story. It is amazing how ofter the creatures seem to get mentioned, having been gone for 65 million years. You would think that you couldn't dig a fence post hole without hitting a dinosaur fossil. The only way to prove the theory of which asteroid it came from, would be to try and match up the iridium samples from Earth with a sample of the suspect. Don't volunteer for that journey during solar maximum. Of course, if another asteroid were to hit, as I once reminded a friend while walking near the Superdome, dinosaurs might once again walk down Poydras Street. (The comets are the ones that could do us in. No time to deflect them.) There would be plenty of time for them to evolve again before the Sun fried Earth as a red giant. How much would the next dinosaurs be like the last bunch? A lot of the last ones walked on two legs. Maybe the next bunch will evolve to be smarter than us, if they can avoid a big asteroid or comet. Luckily, I don't waste a lot of time thinking about them. I can't even remember the first time I became aware of their existence. Anyway, whales are bigger.

Submitted: 9/20/2011 3:18:07 PM (CST)

JOSEPH A'HEARN from MARYLAND said:

It will be interesting to see how far back the ancestry of the "asteroid family tree" can go. Will we be able to tell whether some objects now in the asteroid belt originated in the Kuiper belt instead, or even in the Oort cloud or other solar systems?

Submitted: 9/20/2011 3:01:46 PM (CST)