The unusual asteroid 2201 Oljato: Origins and possible debris trail

Abstract

Potentially hazardous asteroid Oljato has a very eccentric low-inclination orbit of semimajor axis a 2.17 au, placing it just outside 4:1 resonance with Jupiter. Its association with magnetic field anomalies known as Interplanetary Field Enhancements (IFEs) in the solar wind led to speculation of a cometary nature and origin. Spectroscopic work showed that it was instead of silicate E-type typical of the inner asteroid belt or Hungarias. We have investigated the region potentially subject to 4:1 resonant effects and find that resonant pumping of eccentricity e takes place due to the outer planets, with moderate increases in inclination i in non-ejected cases. The outer planets do not, however, cause a change sufficient to move Oljato to its present location from the resonance. With inner planet effects included, the increase in e and i is in most cases reduced, however a diffusion increases, so that such a pumping/scattering mechanism can explain the present orbit of Oljato. IFEs may plausibly be related to a debris cascade involving secondary material along Oljato׳s orbit. We investigate the dynamics of such inferred meteoroids, finding that planetary encounters cause gaps in their distribution along the orbit. The control case of Eros confirms that encounters are needed to cause the gaps, with slow diffusion of secondary material in their absence.