Science | February 22, 2021 1:25 pm

The Strange, Orbital Afterlife of an Apollo-Era Rocket Booster

How scientists traced 2020 SO, a previously unidentified object, to the Surveyor 2 launch back in 1966

Titan IV Nasa 1994
This Titan IV launch in 1994 featured a Centaur rocket booster like the one found in orbit.
NASA/Space Frontiers/Getty Images

Looking back at the early decades of space exploration often involves seeing images and film of massive rocket boosters conveying vehicles into orbit and beyond. The afterlives of these rockets haven’t been nearly as well-documented, though it’s worth mentioning that one of SpaceX’s more innovative features involves making rocket boosters reusable.

It turns out that some rocket boosters have stuck around long after the missions they were used for have been successfully completed. At least one of them would have a particularly fascinating story to tell, if rocket boosters could talk. (Maybe that’s in SpaceX’s next upgrade.)

A new article by Mark Strauss at Air & Space tells the story of an object floating in space and detected by astronomers, dubbed 2020 SO. Late last year, scientists began to speculate that 2020 SO might be part of a Centaur rocket booster used for a NASA mission decades earlier. Now, that speculation has become a certainty.

Before 2020 SO fell into Earth’s orbit, it has been orbiting the sun — and doing so in a way that indicated to scientists that it was hollow. The director of the Center for Near-Earth Object Studies, Paul Chodas, reverse-engineered the object’s trajectory, which suggested that it could have come from Earth in 1966. The timing matched up with the launch of Surveyor 2, which malfunctioned and crashed into the moon resulting in its booster veering off into space.

The University of Arizona’s Vishnu Reddy handled the final pieces of the puzzle, confirming that 2020 SO was made from stainless steel and matched the visible wavelength spectra of other Centaur boosters. It’s a fascinating solution to a long-running mystery.

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