Earth is about to get a temporary mini-moon — and this one might be space junk. Researchers are tracking an object that looks like it will be captured by Earth’s gravity for just a few months this winter before safely heading back out into the Solar System. It might be a standard asteroid, but some astronomers say that the mystery object’s path indicates that it could be a part of a 1960s era rocket.
“I’m pretty jazzed about this,” Paul Chodas, the manager of NASA’s Center for Near Earth Object Studies told The Associated Press. Chodas is one of the world’s leading experts on asteroids and has been on the lookout for returning space debris for decades, he told the AP.
The object was first identified last month by researchers in Hawaii. They named it 2020 SO, and designated it as a near-earth asteroid.
Asteroid 2020 SO may get captured by Earth from Oct 2020 - May 2021. Current nominal trajectory shows shows capture through L2, and escape through L1. Highly-chaotic path, so be prepared for lots of revisions as new observations come in. @renerpho @nrco0e https://t.co/h4JaG2rHEd pic.twitter.com/RfUaeLtEWq— Tony Dunn (@tony873004) September 20, 2020
But the object is a little weird for a typical asteroid. It’s moving relatively slowly, it’s on the same plane as the Earth, and it’s got a nearly circular orbit around the Sun, just like Earth. All those characteristics are “red flags,” according to Chodas, which could indicate that the object was once launched from Earth.
“That’s precisely the kind of orbit that a rocket stage separated from a lunar mission would follow, once it passes by the Moon and escapes into orbit about the Sun. It’s unlikely that an asteroid could have evolved into an orbit like this, but not impossible,” Chodas told CNN in September.
The object appears to be 26 feet long, about the same size as the upper stage of a Centaur rocket. That, plus its path through the Solar System, makes it a good match for the rocket booster that helped launch NASA’s Surveyor 2 Mission in 1966. The mission itself was a failure. After it launched successfully, one of the thrusters onboard the spacecraft malfunctioned, sending it careening into the Moon.
The booster that launched the ill-fated spacecraft kept going past the Moon, and out into the Solar System. Researchers will be able to determine if 2020 SO is the booster, and not a space rock once, the object gets a little closer. Boosters like this are made of relatively light metal — it won’t move the same way as a dense rock in space.
Whatever the object is, it’s expected to stay in Earth’s orbit for a few months this winter before continuing on its way. Only a few of these temporarily captured objects (or, informally, mini-moons) have been observed, including one that hung around between 2006 and 2008, and another one that lingered un-noticed for about a year, before departing in March 2020.