Transient Jupiter Co-orbitals from Solar System Sources

We demonstrate dynamical pathways from main-belt asteroid and Centaur orbits to those in co-orbital motion with Jupiter, including the retrograde (inclinationi > 90 degrees) state. We estimate that, at any given time, there should be similar to 1 km-scale or larger escaped asteroid in a transient direct (prograde) orbit with semimajor axis near that of Jupiter's (a a(J)), with proportionally more smaller objects as determined by their size distribution. Most of these objects would be in the horseshoe dynamical state, and are hard to detect due to their moderate eccentricities (spending most of their time beyond 5 au) and longitudes relative to Jupiter being spread nearly all over the sky. We also show that 1% of the transient asteroid co-orbital population is onretrogradeorbits with Jupiter. This population, like the recently identified asteroid (514107) 2015 BZ(509), can spend millions of years witha a(J)including tens or hundreds of thousands of years formally in the retrograde 1:-1 co-orbital resonance. Escaping near-Earth asteroids (NEAs) are thus likely the precursors of the handful of known high-inclination objects witha a(J). We compare the production of Jovian co-orbitals from escaping NEAs with those from incoming Centaurs. We find that temporary direct co-orbitals are likely dominated by Centaur capture, but we only find production of (temporary) retrograde Jovian co-orbitals (including very long-lived ones) from the NEA source. We postulate that the primordial elimination of the inner solar system's planetesimal population could provide a supply route for a metastable outer solar system reservoir for the high-inclination Centaurs.