The asteroid belt as a window into the solar system's past

The modern asteroid belt contains a complicated record of the solar system’s first large objects that is highly polluted after billions of years of collisional grinding. Moreover, the peculiar distribution of eccentric and inclined orbits in the belt was acquired via interactions with the giant planets during the solar system's earliest formative epochs. The quality of our science is heavily limited by the computational power available. For the N-body simulations I use in my research, this limits the size of the window of time I can investigate, and the number of objects I can use. GPUs (graphics processing units, similar to those in your Xbox!) are a powerful tool for overcoming these issues, and are becoming increasingly available to computational researchers. GPUs allow certain processes to be performed in parallel; thus enabling faster simulations with more objects. To understand the consequences of the early instability model in the asteroid belt, I leverage the GPU code GENGA to study the Asteroid Belt with realistic size resolution. The accompanying video shows a simulation where the asteroid belt is modeled using 3000 fully self-interacting asteroids with masses equivalent to that of the largest asteroid, Ceres. In Clement et al. (2019a), we found that the instability can deplete the asteroid belt of 99-99.9% of its mass. However, the migration the giant planets' tends to fossilize a population of asteroids with high-inclinations in the inner main belt that are not observed (top panel of figure below).

The orientation of asteroid orbits in the asteroid belt precess in physical space on timescales of ~10,000 years due to gravitational perturbations from the massive Jupiter and Saturn (i.e.: the shape of the orbit reorients much like the precession of a spinning top). Interestingly, a gap in the distribution of precession rates is fossilized throughout the asteroid belt (roughly between the two horizontal lines in the accompanying figure). In Clement et al. (2020a), we showed that this void is related to the inclination problem described above. Moreover, this gap was carved during the final phase of Saturn's orbital migration, and the only asteroids currently between the two red lines were implanted later as the result of asteroid break-ups. By accounting for this final migration, our GPU accelerated formation models yielded markedly improved final systems of asteroids in terms of the distribution of their orbital inclinations (compare the middle panel of the above figure to the real belt depicted in the bottom panel).