Global map of Bennu

Week Four: Ninth Anniversary Fund-Raising Drive for Behind the Black

The fourth week of my annual anniversary fund-raising campaign for Behind the Black has begun.

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Global map of Bennu

The OSIRIS-REx science team today released a global map of Bennu, compiled from images taken in December.

The map is above. It was released with no commentary. In comparing it with this global map of Ryugu, created by the Japanese probe Hayabusa-2, I am struck by how much both asteroids resemble each other.

This fact is in many ways a first. Since the first planetary probes left Earth in the 1960s the one reliable expectation that has consistently proven true is that no planetary object, be it planet, dwarf planet, moon, asteroid, or comet, was going to resemble any other planetary object. Each has been entirely unique, and unique in very startling and obvious ways.

Ryugu and Bennu represent the first planetary objects that actually look pretty much the same. Scientist will of course be able to note differences, but overall these objects clearly belong to a specific class of asteroids, which in this case is the rubble pile.

In a sense, this similarity marks a significant advancement in our knowledge. Up until now, we had observed so few objects that our knowledge base wasn’t large enough to start seeing patterns within our general classifications of planet, asteroid, or comets. That is now finally changing.



  • mpthompson

    I always thought the Moon and Mercury closely resemble each other. Perhaps that resemblance is just superficial?

  • mpthompson: You have a point. They do resemble each other, though not as much as one might think if you limit your look to just a quick glance.

    I could say that this is the exception that proves my rule. Yeah, I could say that. Yup. That’s my story and I’m sticking to it.

  • Orion314

    I’ve always viewed Uranus & Neptune as kindred.

  • Dick Eagleson


    Superficially similar, but the Moon’s average density is 3.34 g/cc while that of Mercury is 5.43 g/cc – almost the same as Earth’s 5.52g/cc.

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