S8 Ep884: When the spacecraft arrived at Bennu in late 2018, the team was shocked to find a rugged, boulder-strewn surface instead of the expected sandy "beach." Bennu revealed itself as a "trickster" and an "active asteroid," frequently ejecting rock particles int

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John Batchelor

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🗓️ 18 May 2026

⏱️ 14 minutes

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Summary

When the spacecraft arrived at Bennu in late 2018, the team was shocked to find a rugged, boulder-strewn surface instead of the expected sandy "beach." Bennu revealed itself as a "trickster" and an "active asteroid," frequently ejecting rock particles into space like "popcorn." These surprises forced the team to abandon their original laser-guided landing plan for a more sophisticated "Bullseye TAG" autonomous system. During the eventual sample collection at the "Nightingale" site, the asteroid's surface behaved like a fluid; the collector plunged so deep it became overfilled, causing precious material to leak into space. (3/4)
SEPTEMBER 1963

Transcript

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0:00.0	This is CBSI in the world. I'm John Patcher, visiting with Professor Dante S. Loretta.
0:10.5	His new book is The Asteroid Hunter, a scientist journey to the dawn of our solar system.
0:16.4	We're now in space. The asteroid Benu is approaching perihelian, meaning that it's close to the sun.
0:27.1	The perfectly built Osiris rec spacecraft has approached it over a time period in which they
0:34.7	count out at the Mike Drake building in Arizona.
0:38.0	They count each day, 438, 437, 436.
0:42.4	Well, it's just days left.
0:45.2	And we're now accompanying Benu.
0:49.0	However, there are surprises.
0:51.0	And one surprise is there's no beach.
0:54.1	What beach, professor?
0:55.0	What were you looking for?
0:57.0	Yeah, we mentioned that we discovered the asteroid in 1999, and it comes close to the Earth every six years.
1:04.0	So in 2005, when we selected it as our target, we performed an unprecedented telescopic astronomical
1:10.0	astronomical campaign.
1:11.6	And two key instruments that we used were the Erescebo planetary radar system, which was based in Puerto Rico,
1:18.6	and the Spitzer Space Telescope, which is part of NASA's Great Observatories program.
1:23.6	Both of those suggested the average size of particles on the surface of the asteroid
1:29.3	was smaller than an inch or so. And when you have two pieces of information that give you the same
1:35.5	conclusion, you start to build a lot of scientific confidence. And we thought that meant it was
1:40.1	going to be gravelly or sandy on the surface and very easy to pick up particles.
1:44.7	So when we talked about those reviews in front of NASA, I got up there and presented all the
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