Characterization of the ejecta from NASA/DART impact on Dimorphos: observations and Monte Carlo models

TL;DR

This study combines ground and HST observations with Monte Carlo models to characterize the dust ejecta from NASA's DART impact on Dimorphos, revealing particle sizes, velocities, and ejected mass.

Contribution

It provides the first detailed characterization of ejecta properties using combined observational data and modeling, including particle size distribution and ejection dynamics.

Findings

Particle size distribution follows a broken power-law with indices -2.5 and -3.7.

Ejected dust particles range from 1 micron to 5 centimeters.

Total ejected dust mass is estimated at approximately 6 million kilograms.

Abstract

The NASA/DART (Double Asteroid Redirection Test) spacecraft successfully crashed on Dimorphos, the secondary component of the binary (65803) Didymos system. Following the impact, a large dust cloud was released, and a long-lasting dust tail was developed. We have extensively monitored the dust tail from the ground and from the Hubble Space Telescope (HST). We provide a characterization of the ejecta dust properties, i.e., particle size distribution and ejection speeds, ejection geometric parameters, and mass, by combining both observational data sets, and by using Monte Carlo models of the observed dust tail. The differential size distribution function that best fits the imaging data was a broken power-law, having a power index of --2.5 for particles of r$\le$ 3 mm, and of --3.7 for larger particles. The particles range in sizes from 1 $\mu$m up to 5 cm. The ejecta is characterized by two components, depending on velocity and ejection direction. The northern component of the double tail, observed since October 8th 2022, might be associated to a secondary ejection event from impacting debris on Didymos, although it is also possible that this feature results from the binary system dynamics alone. The lower limit to the total dust mass ejected is estimated at $\sim$6$\times$10$^6$ kg, half of this mass being ejected to interplanetary space.