Elliptical ejecta of asteroid Dimorphos is due to its surface curvature
Masatoshi Hirabayashi, Sabina D. Raducan, J. M. Sunshine, T. L. Farnham, J. D. P. Deshapriya, Jian‐Yang Li, G. Tancredi, Steven R. Chesley, R. T. Daly, C. M. Ernst, Igor Gai, P. H. Hasselmann, Shantanu P. Naidu, Hari Nair, E. E. Palmer, Dany Waller, Angelo Zinzi, Harrison Agrusa, Brent W. Barbee, Megan Bruck Syal, G. S. Collins, T. M. Davison, Mallory E. DeCoster, Martin Jutzi, Kathryn M. Kumamoto, Nicholas Moskovitz, Joshua Lyzhoft, S. R. Schwartz, Paul Abell, O. S. Barnouin, N. L. Chabot, Andrew F. Cheng, E. Dotto, Eugene G. Fahnestock, Patrick Michel, D. C. Richardson, A. S. Rivkin, A. M. Stickle, Cristina A. Thomas, Joel Beccarelli, J. R. Brucato, M. Dall’Ora, Vincenzo Della Corte, E. Mazzotta Epifani, Simone Ieva, Gabriele Impresario, Stavro Ivanovski, Alice Lucchetti, Dario Modenini, M. Pajola, P. Palumbo, Simone Pirrotta, Giovanni Poggiali, A. Rossi, Paolo Tortora, Filippo Tusberti, Marco Zannoni, Giovanni Zanotti, Fabio Ferrari, D. A. Glenar, Isabel Herreros, Seth A. Jacobson, Özgür Karatekin, M. Lazzarin, Ramin Lolachi, Michael P. Lucas, Rahil Makadia, F. Marzari, Colby C. Merrill, A. Migliorini, Ryota Nakano, Jens Ormö, Paul Sánchez, Cem Berk Senel, Stefania Soldini, T. J. Stubbs
Abstract
Kinetic deflection is a planetary defense technique delivering spacecraft momentum to a small body to deviate its course from Earth. The deflection efficiency depends on the impactor and target. Among them, the contribution of global curvature was poorly understood. The ejecta plume created by NASA’s Double Asteroid Redirection Test impact on its target asteroid, Dimorphos, exhibited an elliptical shape almost aligned along its north-south direction. Here, we identify that this elliptical ejecta plume resulted from the target’s curvature, reducing the momentum transfer to 44 ± 10% along the orbit track compared to an equivalent impact on a flat target. We also find lower kinetic deflection of impacts on smaller near-Earth objects due to higher curvature. A solution to mitigate low deflection efficiency is to apply multiple low-energy impactors rather than a single high-energy impactor. Rapid reconnaissance to acquire a target’s properties before deflection enables determining the proper locations and timing of impacts. Double Asteroid Redirection Test (DART) mission impact on asteroid Dimophos resulted in an elliptical ejecta plume. Here, the authors show that this elliptical ejecta is due to the curvature of the asteroid and makes kinetic momentum transfer less efficient.