This past weekend, people in Mexico noticed a bright streak moving across the sky and breaking into pieces. People all over Twitter thought it was an incoming meteor, but there are several important differences between a meteor and what it actually was – space debris.Meteors move much faster than space debris, crossing the sky in seconds, and can come in any direction. Space debris typically moves slower, crossing the sky in minutes because it’s in Earth orbit, not coming in from a solar orbit. Also, except for very rare circumstances, all space debris will reenter going from west to east because that’s the direction almost all rockets launch.

The particular space object which made a bright return to Earth Saturday afternoon was the second stage from a Falcon 9 rocket that, in 2017, sent a satellite into super synchronous transfer orbit, a type of geostationary transfer orbit with the apogee far higher than geostationary altitude.

After satellite deployment, it was vented of all remaining propellant and battery chemistry and left to drift in orbit instead of being deorbited. This is the current industry practice. It spent the next five years slowly decaying through atmospheric drag. It was tracked since launch, and predictions on when it would reenter were made by the U.S. government for several days prior to the event.

The initial Twitter reports were matched up with this prediction by astronomer Jonathan McDowell, who we’ve had on our show before, among others, to confirm the identity of the particular piece of space debris. Space junk typically burns up during reentry, though the pressurized helium bottles called Composite Overwrap Pressure Vessels used on Falcon 9 second stages have been known to survive reentry and ground impact mostly intact.

More Information

SpaceX Falcon 9 upper stage breaks up in Earth’s atmosphere, 5 years after launch (Space.com)