近日，美国约翰霍普金斯大学的Andrew F.Cheng研究团队首次确定了，美国航空航天局（NASA）双小行星重定向测试(DART)任务对小行星Dimorphos进行动能撞击后的动量转移。相关研究成果于2023年3月1日在国际权威学术期刊《自然》上发表。

该研究团队首次确定了DART任务进行动能撞击时转移给小行星的动量。根据双星轨道周期的变化，研究人员发现Dimorphos的轨道速度沿轨道方向瞬间减少了2.70±0.10 mm s^-1，这表明由于撞击产生的抛射流的反冲作用而实现了动量转移的增强。对于体密度为1500 ~ 3300 kg m^-3范围的Dimorphos，研究人员发现动量增强因子β的期望值取决于Dimorphos的质量，范围在2.2至4.9之间。如果假定Dimorphos和Didymos的密度相等，均为2400 kg m^-3， 则β值为3.61+0.19或3.61-0.25(1σ)。这些β值表明，与DART事件相比，逸出的撞击抛射物传递给Dimorphos的动量明显更多。因此，DART动能撞击在偏转小行星Dimorphos方面非常有效。

研究人员表示，美国航空航天局（NASA）双小行星重定向测试(DART)任务于2022年9月26日23:14 UTC对小行星Dimorphos(双小行星(65803)Didymos的卫星)进行了动能撞击，作为行星防御测试的一部分。DART是第一个在与行星防御相关的尺寸和速度范围内进行的小行星超高速撞击实验，旨在验证动能撞击作为小行星偏转的一种手段。

附：英文原文

Title: Momentum Transfer from the DART Mission Kinetic Impact on Asteroid Dimorphos

Author: Cheng, Andrew F., Agrusa, Harrison F., Barbee, Brent W., Meyer, Alex J., Farnham, Tony L., Raducan, Sabina D., Richardson, Derek C., Dotto, Elisabetta, Zinzi, Angelo, Della Corte, Vincenzo, Statler, Thomas S., Chesley, Steven, Naidu, Shantanu P., Hirabayashi, Masatoshi, Li, Jian-Yang, Eggl, Siegfried, Barnouin, Olivier S., Chabot, Nancy L., Chocron, Sidney, Collins, Gareth S., Daly, R. Terik, Davison, Thomas M., DeCoster, Mallory E., Ernst, Carolyn M., Ferrari, Fabio, Graninger, Dawn M., Jacobson, Seth A., Jutzi, Martin, Kumamoto, Kathryn M., Luther, Robert, Lyzhoft, Joshua R., Michel, Patrick, Murdoch, Naomi, Nakano, Ryota, Palmer, Eric, Rivkin, Andrew S., Scheeres, Daniel J., Stickle, Angela M., Sunshine, Jessica M., Trigo-Rodriguez, Josep M., Vincent, Jean-Baptiste, Walker, James D., Wnnemann, Kai, Zhang, Yun, Amoroso, Marilena, Bertini, Ivano, Brucato, John R., Capannolo, Andrea, Cremonese, Gabriele, DallOra, Massimo, Deshapriya, Prasanna J. D., Gai, Igor, Hasselmann, Pedro H., Ieva, Simone, Impresario, Gabriele, Ivanovski, Stavro L., Lavagna, Michle, Lucchetti, Alice, Epifani, Elena M., Modenini, Dario, Pajola, Maurizio, Palumbo, Pasquale, Perna, Davide, Pirrotta, Simone, Poggiali, Giovanni, Rossi, Alessandro, Tortora, Paolo, Zannoni, Marco, Zanotti, Giovanni

Issue&Volume: 2023-03-01

Abstract: The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense, intended to validate kinetic impact as a means of asteroid deflection. Here we report the first determination of the momentum transferred to an asteroid by kinetic impact. Based on the change in the binary orbit period, we find an instantaneous reduction in Dimorphos’s along-track orbital velocity component of 2.70 ± 0.10 mm s^–1, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact. For a Dimorphos bulk density range of 1,500 to 3,300 kg m^–3, we find that the expected value of the momentum enhancement factor, β, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg m^–3, β=3.61+0.19或3.61-0.25(1σ). These β values indicate that significantly more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos.

DOI: 10.1038/s41586-023-05878-z

Source: https://www.nature.com/articles/s41586-023-05878-z