How a long-gone Apollo rocket returned to Earth

On September 3, 2002, amateur astronomer Bill Yeung discovered an object that he believed was a never-before-seen asteroid in a rapid orbit around Earth. While it’s easy for massive planets such as Jupiter to frequently capture objects like asteroids and comets, Earth is smaller and has less gravitational oomph with which to influence interplanetary passersby.

Yeung’s discovery, formally named J002E3, became the focus of an intense analysis with a unique result. The object was not an asteroid captured by Earth in a cosmic game of coincidence. This was a relic of humanity’s space race: an Apollo-era rocket that had been placed in orbit around the Sun — and then returned to Earth.

An unusual discovery

Yeung was already well known in astronomy circles for his prolific discovery of other asteroids — J002E3 was simply one more to add to his collection. But astronomers at the Minor Planet Center quickly realized that J002E3 was not an asteroid. Its unusual orbit made some suspect that it was, in fact, human-made — a leftover piece of space hardware.

But an analysis of recent launches did not identify any possible candidates for the source of the object. Scientists at the Jet Propulsion Laboratory (JPL) in Pasadena, California, tracing back the object’s trajectory, discovered that it had been captured in April 2002 into Earth orbit from an orbit around the Sun that was similar to Earth’s. Backtracking even further, the object appeared to have gotten into its Sun-circling orbit after originally escaping Earth orbit all the way back in February 1971.

This gave researchers some potential clues as to the origin of J002E3.

Covered in paint? 

Another team of scientists from the University of Arizona and MIT performed a spectroscopic analysis of J002E3, looking at the light it reflected to search for chemical fingerprints to determine what it was made of. They made a startling discovery: J002E3 appeared to be covered in paint — specifically, white, titaniumoxide (TiO2) paint. According to Kira Jorgensen Abercromby at California Polytechnic State University, who also studied J002E3 while at the Air Force Maui Optical & Supercomputing observatory, “What we saw were features in the spectral data that matched other upper-stage rocket bodies launched during a similar time frame [to the Apollo missions] and the data also matched typical features found in organic paints that looked like TiO2.”

This information pointed toward a very specific object as the identity of J002E3: a spent third stage from an Apollo-era Saturn V rocket, which were historically covered in this specific kind of paint.

The massive Saturn V propelled the Apollo astronauts to the Moon and later lofted the Skylab Space Station into orbit around Earth. While 18 complete Saturn V rockets were built, only 13 were ever launched (the rest were built for testing or never used once Apollo’s funding dried up). The Saturn V was a three-stage rocket. The first and second stages of the Saturn V fell back to Earth once they were spent. The third stage, known as the S-IVB, was just under 60 feet (18 meters) in length and, once released, temporarily orbited Earth along with the Apollo spacecraft before being reignited to send its hardware into lunar orbit. Of note, the Apollo 7 mission used the smaller Saturn IB rocket, which also used an S-IVB as a second stage. According to Amy Shira Teitel, host of YouTube’s The Vintage Space, “Without the S-IVB, the Apollo Moon landings couldn't have happened.”