Wednesday, December 14, 2016

Preparing for the Worst: Studying the Impacts of Impacts

A potentially hazardous object headed straight for us. Little time to prepare. Possible mass extinction. Perpetual winter. The rekindling of life. It sounds like, and it is, the stuff of movies. It’s also the stuff of the American Geophysical Union (AGU) Fall Meeting, taking place this week in San Francisco.

To be fair, the meeting brings together nearly 25,000 Earth and space scientists every fall and the thousands of talks and posters cover an enormous range of fascinating topics. But it’s hard to pass up a press conference highlighting what we’ve learned by drilling into the crater caused by the asteroid that wiped out the dinosaurs, immediately followed by a press conference on defending our home planet from such objects.

Image Credit: Public Domain

In the middle of finals and stressful holiday preparations, mass extinction is probably not at the top of your worry list. Luckily for us, scientists around the world spend their days calculating, modeling, and analyzing their way toward a future that minimizes the risk that we will go the way of the dinosaurs—and not just the dinosaurs, but all animals over 55 pounds and 75% of all of the life on Earth. That’s what happened when a giant asteroid hit just off the coast of Mexico about 66 million years ago.

The impact caused a crater some 124 miles across that is now buried under water and limestone, called the Chicxulub crater after a nearby town. This is the most well preserved large impact crater on Earth, as it hasn’t been disturbed by erosion or tectonics. Studying Chicxulub is a way of studying what happened 66 million years ago and how life recovered from that fateful day. It’s also a cautionary tale.

In March and April of 2016, the scientists on Expedition 364 sank their teeth into Chicxulub. A joint project of the International Ocean Discovery Program and the International Continental Scientific Drilling Project, the team inhabited a rig high above the crater, drilling deep into the peak ring formation at its center and analyzing the core. A peak ring is a mountainous, ring-shaped feature that sometimes results from large impacts.

The team published its first scientific results from the drilling project last month in Science, explaining how peak rings form. The composition of their sample tells a dramatic story of huge pressures, high shock, and granite being ripped apart. By understanding how these craters form, we can better estimate the properties of the asteroids that caused them.

At AGU, the team also reported on early evidence of how life within the crater recovered from the devastating impact. Their layered sample contains information on the types of plankton before and at various times after the impact. We still have a lot to learn about why this impact was so catastrophic for so many species, but this work should provide insight moving forward.

This research is a fascinating glimpse into this dark day, but you can also take it as a warning sign. Unlike the dinosaurs, we have advanced technology that can help preserve life in the face of such a threat. Many people are working to raise awareness of this, in hopes of convincing decision makers to invest more heavily in early warning and intervention systems. (You can read about some of these efforts in our Asteroid Day post from earlier this year.)

For NASA scientist Joseph Nuth, defending Earth includes not only searching for asteroids that might be on a collision course with us, something already well underway, but preparing for terrifying surprises. This could include hidden asteroids and, more commonly, comets. Their long orbital periods mean we may not have five years to build and launch a spacecraft capable of knocking a comet off course once the alarm has been raised.

A better plan, he says, is to build and store an observer spacecraft that could be quickly launched to collect key details about the object and an interceptor spacecraft that could be launched later to neutralize the threat. This would require a big investment, but considering the alternative it may be one worth making. (Note that this is Nuth’s scientific recommendation, not a recommendation presented on behalf of NASA administration.)

The conference also included scientists from Lawrence Livermore National Lab (LLNL) working on the techniques for deflecting a threat—a kinetic impactor and a nuclear explosion. With a lot of lead time, you could imagine nudging an asteroid off course by crashing into it with a high-speed spacecraft, this is the kinetic impactor technique. If you don’t have so much time, a nuclear solution becomes your best bet. That doesn’t necessarily mean blowing the object up, although that is a possibility. In many cases, the more ideal approach is to detonate a strategically placed very energetic explosion that slows down or speeds up the object so that we aren’t in the same place at the same time.

Rather than wait until a moment of crisis to figure out a plan of action, scientists are elbow-deep in modeling the possibilities with supercomputers at LLNL and other labs. The physics is complicated and there are lots of unknowns, but our understanding is growing. Scientists are also modeling potential outcomes if we do get hit. Best case scenario if an average-sized asteroid does makes it here? Cross your fingers that it hits or breaks apart over the middle of the ocean. The models indicate that we would see a tremendous splash, but little danger of a Tsunami or catastrophic outcomes.

Avoiding the fate of the dinosaurs is not just luck, we have the unique advantage of living in a place and time in history that can take some control over our future and objects that might be on a path to our destruction. Though, doing so requires careful planning and investing in a solution to a problem that may or may not be imminent. That story might not make for an exciting movie, but it could give us a bit more time to come up with new plot twists.

Kendra Redmond

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