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As Lucy sent more data back to Earth, the researchers discovered something surprising: Selam was not just one moon, it was a contact binary -- or two moons melded together.

The latter turned out to be "an extraordinarily unique and complex body," Merrill said -- a so-called "contact binary" consisting of two lobes that are essentially rubble piles stuck together, and the first of its kind seen orbiting another asteroid.

Contact binary systems seem to be fairly common throughout our solar system, but scientists hadn't seen one orbiting another asteroid prior to Dinkinesh, Lucy's deputy project scientist John Spencer said in the statement.

Apophis is shaped like a peanut shell, a form astronomers call a “contact binary.”

And perhaps most importantly, the contact binary is a member of the “cold classical” family of bodies in the Kuiper Belt—objects in sedate, circular orbits that have scarcely interacted with anything else since their formation more than four billion years ago, at the solar system’s dawn.