Scenarios for the dynamics of comet 67P/Churyumov–Gerasimenko over the past 500 kyr

The complex dynamics of 67P has the typical uncertainties of the Jupiter-family comets. The\udRosetta mission provided a unique opportunity to dissipate them with fresh experimental data.\udWe aim to constrain the residence time of the comet in a dynamics dominated by Jupiter and\udSaturn by comparing statistics of large sets of numerical integrations with assumptions on\udthe erosion experienced by the comet. We integrated backward for 150 kyr 2000 clones of\ud67P selected from preliminary integrations of 500 000 clones. We find that the clones that\uddid not arrive from hyperbolic/parabolic orbits have been mostly in the region dominated by\udJupiter and Saturn in the last 150 kyr; they transit easily between dynamics dominated by\udJupiter, dynamics also dominated by Saturn and, with smaller probability, by Saturn alone.\udMany clones were injected in the Jupiter family from hyperbolic orbits and orbits of large\udperiods P > 500 yr, but none of the clones was injected from a Uranus-dominated dynamics\udthrough sequences of planetary scatterings, while 5 per cent of the clones were injected on this\udroute in 500 kyr. 60 per cent of the clones had already been in an orbit with q < 1.5 au before\ud1959. Compatible with the uncertainties on the long-term model of non-gravitational forces,\udwe conclude that 67P was injected from a cometary reservoir into a dynamics dominated by\udJupiter and Saturn at an epoch that we estimate as being in between 30 and 150 kyr ago; this\udinterval should be extended by considering periods of dormancies