Decameter-sized Earth impactors – I: Orbital properties

Numerous decameter-sized asteroids have been observed impacting Earth as fireballs. These objects can have impact energies equivalent to hundreds of kilotons of TNT, posing a hazard if they impact populated areas. Previous estimates of meteoroid flux using fireball observations have shown an Earth impact rate for decameter-size objects of about once every 2–3 years. In contrast, telescopic estimates of the near-Earth asteroid population predict the impact rate of such objects to be of order 20–40 years, an order-of-magnitude difference. While the cause of this discrepancy remains unclear, tidal disruption of a larger near-Earth body has been proposed as an explanation for these excess decameter-sized impactors. The release in 2022 of previously classified United States Government (USG) satellite sensor data for fireball events has provided a wealth of new information on many of these impacts. Using this newly available USG sensor data, we present the first population-level study characterizing the orbital and dynamical properties of 14 decameter-sized Earth impactors detected by USG sensors since 1994, with a particular focus on searching for evidence of tidal disruption as the cause of the impact rate discrepancy. We find there is no evidence for recent ( ≲ 1 0 4 years) tidal disruption and weak evidence for longer-term tidal disruption in the decameter impactor population, but that the latter conclusion is limited by small number statistics. We also investigate the origins of both the impactor and near-Earth asteroid populations of decameter-sized objects from the main asteroid belt. We find that both populations generally originate from the same source regions: primarily from the ν 6 secular resonance ( ∼ 70 %) with small contributions from the Hungaria group ( ∼ 20 %) and the 3:1 Jupiter mean-motion resonance ( ∼ 10 %). • The telescopically observed decameter near-Earth asteroid population is biased. • There are not enough known Earth impactors to rule out or support the tidal disruption hypothesis. • The decameter impactor and telescopic populations come from the same source regions.