1,1,2,2,4,5- 1Institut Supérieur de l’Aéronautique et de l’Espace (ISAE-SUPAERO), Université de Toulouse, France
- 2IFAC-CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy
- 3Astronomical Observatory Institute, Faculty of Physics and Astronomy, Adam Mickiewicz University ul. Sloneczna 36 60-286 Poznań, Poland
- 4Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
- 5University of Colorado, Boulder, Colorado 80309, USA
The DART impact on Dimorphos caused the ejection from the asteroid of a large amount of debris of varying sizes, ranging from dust to large boulders [1]. A fraction of the low-velocity ejecta that remained in the binary system eventually re-impacted on Didymos as shown by [2] who studied the evolution of a population of large boulders ejected from Dimorphos. These re-impacts, termed sesquinary impacts, potentially altered the surface of Didymos and may have led to the formation of observable features.
In preparation for the Hera mission [3], following the identification of existing boulder tracks on Didymos and using statistical results on sesquinary impacts of ejecta debris combined with the shape model of Didymos, we investigate the fate of large boulders impacting the surface of Didymos at low velocity. We model the dynamics of the boulders after impact, driven by the topography and surface conditions of Didymos, including possible bouncing and assessing the conditions for ballistic lift-off. We statistically investigate the outcome of the sesquinary impacts by varying the key boulder-surface interaction parameters. We find that the displacement of boulders after the initial impact is possible and is driven by the rapid spin of the asteroid, leading to a preferential motion towards the equator and to the potential formation of new boulder tracks formed in the regolith-covered surface. The sesquinary impacts are likely to induce an accumulation of debris in the equatorial region, along with multiple low-velocity craters related to ejection or bouncing. The observation of boulder tracks is most likely from low to mid-latitudes, in the transition zone [4] characterised by low stability and high terrain slopes (Fig. 1). The presence of such surfaces features have the potential to inform on the surface mechanical properties, through interpretation of their location, density and dimensions. The length and starting latitude of tracks can be indicative of the surface friction and terrain stability. New observations by Hera, targeted on the predicted locations will be key to provide evidence supporting those processes and to gather data for subsequent interpretation.
We acknowledge funding support by the ERC GRAVITE project (Grant Agreement N°1087060).
Figure 1: Ground trajectories of impacting boulders on Didymos for three sets of parameters. The blue lines correspond to previously identified tracks [5].
References
[1] Li, J.-Y., Hirabayashi, M., Farnham, T. L., 2023, Nature, 616, 452-456.
[2] Langner, K., Marzari, F., Rossi, A., 2024, Astronomy and Astrophysics, 684, A151.
[3] Michel, P., Küppers, M., Bagatin, A. C., 2022, Sci. J., 3 160.
[4] Barnouin, O. S., Ballouz, R-L., Marchi, S., 2024, Nature Communications, 15, 6202.
[5] Bigot, J., Lombardo, P., Murdoch, N., 2024, Nature Communications, 15, 6204.
How to cite: Bigot, J., Murdoch, N., Rousseau, A., Rossi, A., Langner, K., Marzari, F., Barnouin, O., and Scheeres, D.: Modelling the fate of sesquinary DART ejecta debris impacting on Didymos, Europlanet Science Congress 2026, The Hague, The Netherlands, 7–11 Sep 2026, EPSC2026-96, https://doi.org/10.5194/epsc2026-96, 2026.
