Name: Did This Asteroid Just Turn into a Comet?
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Scientists found bits of rock and dust flying off the asteroid Bennu. Is the OSIRIS-REx spacecraft in danger?

Everything in the solar system is dynamic—you can watch it evolve in real time.

Did This Asteroid Just Turn into a Comet?

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Scientists found bits of rock and dust flying off the asteroid Bennu. Is the OSIRIS-REx spacecraft in danger?

Everything in the solar system is dynamic—you can watch it evolve in real time.

Space & Flight

Did This Asteroid Just Turn into a Comet?Published: November 3, 2020Narrator: While browsing through images of the asteroid, team member Carl Hergenrother notices something strange.Hergenrother: So, I’m blinking through the images, blinking through the images, blinking through the images... and all of a sudden, I come up to one image in particular... where I notice what looks like a star cluster, right off the edge of the asteroid where there shouldn’t be this many bright stars. And these are bright. And I’m looking at it, and I was like, “Well, that’s a pretty big star cluster. It doesn’t look like any of the ones I know.”Narrator: Hoping to get a more detailed view of these strange stars, Carl increases the brightness and contrast of the images… and spots something even more bizarre.Hergenrother: Wow. These extra stars start turning into streaks.Narrator: Tiny streaks… like the streaks that appear in images taken at night on a busy highway.Hergenrother: I had in the back of my mind this little nagging feeling, “Maybe the asteroid is doing something that we didn’t quite recognize.” Narrator: He decides to investigate.Hergenrother: I started drawing lines through these streaks back to the asteroid. It was over probably a half hour of time when the realization—it didn’t come immediately at once, that, oh, what I’m seeing is what I’m seeing. All these streaks are kind of coming from the same place, which means what you’re seeing is a kind of instantaneous event. Boom.Narrator: The glowing dots no longer look like a cluster of stars… but bits and pieces of rock and dust flying off Bennu.Hergenrother: It looks like the asteroid just exploded. So, I walked over, I grabbed Dante and he just turns white.Dante Lauretta: I think literally my jaw hit the floor at that point. It looks like this thing has just turned into a comet and is blasting particles into outer space. So, my first response was, “Is this OK for the spacecraft?” Immediately, we got the spacecraft team in a room to start looking at this information and saying, “OK, do we need to fire the engines and get away from this asteroid, or are we OK to stay in orbit?”Narrator: They can’t immediately tell how big the particles are and worry that one could be moving fast enough to pack a damaging punch if it hits the spacecraft.Coralie Adams: We quickly built up tools to analyze how the particles were moving by observing what the velocities were and the sizes. Narrator: Careful analysis reveals the particles are fairly small—ranging in size from less than an inch up to four inches. And more importantly, they are traveling at a relatively slow speed. Adams: The velocities were low enough for the particles that they would essentially bounce off the spacecraft if they even came close.Lauretta: And then the whole mood of the team changed. It’s like, “OK, we don’t have to worry, now this is a really exciting scientific discovery. What is going on? Bennu is an active asteroid. How can that possibly be?” Hergenrother: This may happen on every single asteroid that’s out there. And it’s just we were the first mission that had the right instrumentation and were at the right distance and were taking the right data to actually detect this, but they all might be doing this. So this may be a common phenomenon everywhere in the solar system.Narrator: What’s causing this phenomenon? Carl has a theory.Hergenrother: It could be as simple as just meteorites hitting the surface constantly. You know, like the meteors you see when you look up in the sky.Derrick Pitts: We might think that the solar system’s done. Everything is settled in place. But that’s not the case. The solar system is still under construction, so to speak. There are still asteroids that collide with other objects.Hergenrother: It isn’t just, you know, asteroids crashing into the Earth and killing the dinosaurs. They’re all crashing into each other, and they’re all breaking up and throwing off pieces. So everything is really dynamic, and you’re just kind of watching the solar system evolve in real time.

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Did This Asteroid Just Turn into a Comet?

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Touching the Asteroid

In a swirl of rocks and dust, OSIRIS-REx probe touches an asteroid

On the Asteroid Bennu, Surprising Activity and Rugged Terrain

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Explore More

Touching the Asteroid

In a swirl of rocks and dust, OSIRIS-REx probe touches an asteroid

On the Asteroid Bennu, Surprising Activity and Rugged Terrain