Potential Themis-family Asteroid Contribution to the Jupiter-family Comet Population

Abstract

Recent dynamical analyses suggest that some Jupiter family comets (JFCs) may originate in the main asteroid belt instead of the outer solar system. This possibility is particularly interesting given evidence that icy main-belt objects are known to be present in the Themis asteroid family. We report results from dynamical analyses specifically investigating the possibility that icy Themis family members could contribute to the observed population of JFCs. Numerical integrations show that such dynamical evolution is indeed possible via a combination of eccentricity excitation apparently driven by the nearby 2:1 mean-motion resonance with Jupiter, gravitational interactions with planets other than Jupiter, and the Yarkovsky effect. We estimate that, at any given time, there may be tens of objects from the Themis family on JFC-like orbits with the potential to mimic active JFCs from the outer solar system, although not all, or even any, may necessarily be observably active. We find that dynamically evolved Themis family objects on JFC-like orbits have semimajor axes between 3.15 au and 3.40 au for the vast majority of their time on such orbits, consistent with the strong role that the 2:1 mean-motion resonance with Jupiter likely plays in their dynamical evolution. We conclude that a contribution from the Themis family to the active JFC population is plausible, although further work is needed to better characterize this contribution.

The physical and dynamical characteristics of the asteroid 4940 Polenov

“…11 is most likely caused by some unidentified high order resonance. Recent studies in Hsieh et al (2020) illustrated that Themis family members are capable to escape via some of the strongest resonances in the family and join the population of Jupiter family comets. Polenov, a quiet member of the family is not one of such escapers.…”

Using Atmospheric Impact Data to Model Meteoroid Close Encounters

“…The SD is cold, likely very primitive and volatile-rich, with larger eccentricities than the classical Kuiper Belt (Gomes et al 2008). Other sources from within the MB have also been proposed to partially supply material to the JFCs (Fernández et al 2002;Kim et al 2014;Fernández & Sosa 2015;Hsieh et al 2020). This can occur as a result of outward diffusion from the MB via mean-motion resonances (MMR), primarily the 2:1 MMR (3.27 au).…”

“…This can occur as a result of outward diffusion from the MB via mean-motion resonances (MMR), primarily the 2:1 MMR (3.27 au). Other outer-MB resonances such as the 9:4 and 11:5 MMRs have been suggested to be able to produce a modest amount of objects on JFC-like orbits (Fernández et al 2014;Fernández & Sosa 2015;Hsieh et al 2020). Studies have additionally found that terrestrial planets (particularly Earth and Venus) may play an important role by perturbing MB objects onto JFC-like orbits (Fernández et al 2002;Hsieh et al 2020).…”

“…Therefore, the probability of re-observing these gravitationally scattered objects may be worth consideration. Close encounters with the Earth could provide an additional way to transfer material from the MB to JFC-like orbits (Fernández & Sosa 2015;Hsieh et al 2020).…”

“…These authors argued that these objects could have migrated into this region via non-gravitational effects (such as the Yarkovsky effect) due to their smaller size, higher reflectance, and smaller perihelion distance. These objects can also be transferred to JFC-like orbits directly via MMRs in the outer MB (like the 2:1 and 9:4 MMRs) (Fernández et al 2002(Fernández et al , 2014Fernández & Sosa 2015;Hsieh et al 2020). While most outer-MB objects are dark with low-albedos (p v < 0.1), some higher-albedo objects have also been observed to exist (Masiero et al 2014).…”