Los Alamos National Labs with logo 2021

Collision course

Could scientists deflect an asteroid headed toward Earth?
July 18, 2019
A person points at part of a simulation of an asteroid hitting Earth.

Standing in the Cave Automatic Virtual Environment at the Los Alamos Super Computing Center, scientists interact with simulations of the asteroid that created the Chicxulub crater on the Yucatan Peninsula in Mexico. The asteroid’s impact and resulting climate disruption, which occurred approximately 66 million years ago, likely caused the dinosaurs—and most other plant and animal species on Earth—to go extinct.


“If we prepare well, then for the first time, our species could prevent a major natural disaster.”- Cathy Plesko

An asteroid crashing into Earth is extremely unlikely—but not unprecedented. Sixty-five million years ago, such an event occurred and caused the dinosaurs to go extinct.

Today, to prevent humans from experiencing the same fate, scientists use sophisticated telescopes to monitor the nearly 20,000 asteroids and other near-Earth objects (NEOs) that are on a possible trajectory to collide with our planet.

But what good is monitoring without a plan?

Enter planetary defender Cathy Plesko, a computational physicist at Los Alamos who studies ways to alter an NEO’s flight path. Recently, Plesko studied an asteroid named Bennu, which is as wide as the Empire State Building is tall and weighs as much as 800 aircraft carriers. Bennu approaches Earth once every six years, making it a perfect test case (even though it has only a 1 in 2,700 chance of hitting Earth, about 100 years from now).

“We used computer models to study two ways of pushing Bennu off course: smashing a spacecraft into the asteroid or detonating a nuclear device from several hundred yards away,” Plesko says. “We fed the best estimates of Bennu’s shape, composition, mass, and strength into our computer models and predicted what would happen in each scenario.”

Smashing a spacecraft into Bennu seemed like the best bet, even though it would mean launching a spacecraft 10–25 years before the predicted impact. To further test this concept, NASA—working with Plesko—has designed the Double Asteroid Redirection Test (DART) spacecraft, which will launch in 2020. In 2022, DART is expected to crash into an asteroid called Didymos B at the speed of 6 kilometers per second—enough to shift the asteroid’s orbital path a fraction of 1 percent (but not enough to knock Didymos B onto a collision course with Earth).

“I’m glad we’re doing this research now while we can take the time to carefully study the problem and triple-check our models without the pressure of a specific, potentially hazardous object coming at us,” Plesko says. “If we prepare well, then for the first time, our species could prevent a major natural disaster. We can’t yet push a hurricane off course, cork a volcano, or lock an earthquake-prone fault, but in a few years, we could be ready to stop an asteroid in its tracks.” 

A woman holding a microphone speaks on a stage.

In April 2019, Cathy Plesko traveled to the Planetary Defense Conference in Washington, D.C., where she participated in an emergency response drill in which experts practiced their response to an incoming asteroid. “Like a fire drill, we practiced our roles and tested new technology and scientific data to see how it changed what we thought the best response would be,” she says.