As soon as he saw the data, Paul Chodas knew something was strange about the near-Earth object that had been designated 2020 SO.

As head of NASA's Center for Near-Earth Object Studies at the Jet Propulsion Laboratory in California, Chodas evaluates observations of these objects every day.

Now, nearly a month of ongoing observations have confirmed that 2020 SO is moving more like a spent rocket stage than a space rock, buffeted by simply the sunlight hitting it.

"Our latest orbit calculations for this object clearly show that it is being affected by non-gravitational forces, presumably solar radiation pressure," he wrote in an email update, calling those calculations "very strong evidence" that the object is not a space rock.

But he didn't need the ongoing observations to suspect that the erstwhile space rock was actually human debris, the spent Centaur upper stage of the rocket that, in 1966, sent a NASA mission called Surveyor 2 to the moon.

Instead, Chodas said, 2020 SO's orbit shouts that it's a rocket body from a mission to the moon?

In particular, 2020 SO looks like an object that was trying to land a spacecraft on the moon — gently, and therefore not particularly fast.

"So the rocket body missed the moon and went into orbit around the sun, just barely." (Meanwhile, the Surveyor 2 spacecraft itself botched the soft landing and crashed into the lunar surface.).

That's what caused the slow, near-Earth orbit that so stuck out to Chodas.

"That's why I was suspicious in the first place that this could be a rocket body, and from a lunar mission," he said.

But between the later launch date, the details of the trajectory needed to land softly on the moon rather than simply orbit it, and the relative size of the potential rocket bodies at play, Chodas was soon confident that 2020 SO is actually the Centaur upper stage used to launch NASA's Surveyor 2 mission on Sept.

"This orbit is known so accurately that I can be very sure of the energy with which the rocket left the moon back in 1966, and the direction and geometry," Chodas said during the original interview.