Study warns space debris could complicate 2029 Apophis flyby observations
Asteroid Apophis will pass within 32,000 km of Earth in April 2029, and researchers say a small chance of collision with geostationary debris could obscure scientific measurements.
Asteroid 99942 Apophis, about 370 metres across, is set to swing past Earth at a distance of less than 32,000 kilometres in April 2029. While calculations confirm the rock poses no impact threat, a new study published in The Planetary Science Journal highlights a different risk: a possible encounter with human-made debris in the geostationary orbit region.
Physicist Giulia Schettino and astrodynamicist Alessandro Rossi of the Italian National Research Council examined whether objects orbiting at roughly 36,000 kilometres could intersect Apophis’s trajectory. Rossi, who specializes in both space debris and asteroid dynamics, said he initially expected “a null experiment” with no interactions, but simulations revealed a small but non-zero probability of a collision.
The researchers modeled the asteroid’s path alongside known and estimated unseen debris in GEO. In most scenarios the asteroid passes unharmed, but a rare impact could create a modest crater and ejecta plume. While such an event would not significantly alter Apophis’s orbit, it could complicate the interpretation of data from ESA’s RAMSES mission and NASA’s OSIRIS-APEX spacecraft, which aim to study how Earth’s gravity reshapes the asteroid during the flyby.
"The most important thing to stress is that any impact on the asteroid would not alter its orbit in a significant way," Rossi explained.
"There is also the possibility that the instruments that RAMSES should place on the surface (gravimeter and seismometer) will detect a signal from the impact."
The authors stress that debris in the geostationary belt is sparse, reducing the chance of a cascade of further collisions. Nonetheless, the study underscores gaps in knowledge of small, untracked objects at high altitudes. Rossi noted that upcoming European surveillance telescopes are intended to improve monitoring of high-Earth-orbit debris in the years leading up to the encounter.
The findings aim to ensure that the 2029 flyby yields clear scientific insights into asteroid dynamics without unintended interference from human-made space junk.