Spacecraft encounter with asteroid Bennu is test run for defending Earth

On Dec. 3, the NASA spacecraft OSIRIS-REx arrived at its destination of the near-Earth asteroid Bennu. During the next year, it will orbit the asteroid to search for the best places to land and scoop up samples before eventually returning them to Earth in 2023.

Why it matters: Analyzing Bennu may help scientists learn more about the asteroid's composition, which could lead to new discoveries about how life evolved in the universe.

But there's another reason researchers are interested in the contents of this space rock: They want to learn more about how they might have to, on short notice, divert, deflect or destroy an asteroid that's on a potentially devastating collision course with Earth.

The multi-institution research team has modeled a possible planetary defense mission against Bennu, based on the limited information they had about the small space object, according to Cathy Plesko, a research scientist in applied physics at Los Alamos National Laboratory.

• They did this to help improve their modeling, not because they truly believe Bennu to be a threat to Earth, she adds.

The computer models they used, Plesko tells Axios, gave them a good guess at the shape and composition of the asteroid.

• New data from the close encounter with Bennu can allow the team to refine their models.
• Already there are some surprises, Plesko says, including the finding that the surface of Bennu is comprised of rubble tile with big boulders. The textured surface was not in the team's initial models and will require adjustments to be made in their models.

What's next: A basic task for scientists is to determine how uncertain their models are, just in case they're needed to save humanity from an extinction-level asteroid.

• In all, there are 2 dozen groups of researchers working on this problem, with Los Alamos, Lawrence Livermore and Sandia National Laboratories all involved.
• Plesko says planetary defense is a new field but has made progress in detecting potentially destructive asteroids, for example.

However, without a mission-ready spacecraft or plan, if we were to find an object on a collision course with Earth tomorrow, Plesko says, “We’d still be pretty hard-pressed to stop it from happening.”