Long-Term Evolution of Dimorphos’s Dust Tail Created by the DART Impact

The objectives of this program are to:

1. Constrain the size and size distribution of large (> 1 mm) ejecta particles;
2. Search for large ejecta boulders > 5 m radius embedded in the tail;
3. Characterize the dynamic processes of dust in the binary system from tail morphology;
4. Compare the Dimorphos’s tail with those of natural asteroids associated with episodic, impulsive dust release.

We will use 9 orbits to monitor the dust tail of asteroid Dimorphos created by the DART impact with WFC3/UVIS over 6 months from January 19 to early July  2023. We will analyze the temporal evolution of the tail, including the photometric evolution of the near-asteroid region, the change of tail orientation, brightness, and brightness distribution in order to constrain the dynamic evolution of relatively large and slow dust in the ejecta. With these measurements, we will model the dynamical process of the ejecta particles using numerical simulations. The numerical code will be set up with the initial conditions of the ejecta dust constrained from observations, including the particle size and size distribution. We will explore a range of various ejecta initial speed and speed distribution using the constraints from impact process to match the observed temporal evolution of the tail. Finally, the constraints to the large ejecta particles will help the DART mission to refine the total ejecta mass and velocity-mass distribution measurements, contributing to the estimate of momentum transfer coefficient. We will also compare the tail evolution with the previously observed tails of active asteroids to provide context and gain insight about the understanding of nature active asteroids.