Planetary Science Institute, Tucson, AZ, USA.
Department of Aerospace Engineering, Department of Geosciences, Auburn University, Auburn, AL, USA.
Nature. 2023 Apr;616(7957):452-456. doi: 10.1038/s41586-023-05811-4. Epub 2023 Mar 1.
Some active asteroids have been proposed to be formed as a result of impact events. Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA, in addition to having successfully changed the orbital period of Dimorphos, demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T + 15 min to T + 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact. The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact.
一些活动小行星被认为是由于撞击事件而形成的。由于活动小行星通常只是在它们的尾巴完全形成后才被偶然发现，因此，撞击抛出物如何演变成尾巴的过程，据我们所知，尚未被直接观察到。美国宇航局的双小行星重定向测试（DART）任务除了成功改变了孪发小行星的轨道周期外，还在精确已知的条件下展示了小行星因撞击而被激活的过程。在这里，我们报告了哈勃太空望远镜对 DART 撞击抛出物的观测结果，从撞击时间 T+15 分钟到 T+18.5 天，空间分辨率约为 2.1 公里/像素。我们的观测结果揭示了抛出物的复杂演化过程，最初由 Didymos 双星系统和抛出的尘埃之间的引力相互作用主导，随后由太阳辐射压力主导。速度最低的抛出物通过一条持续的尾巴分散开来，这条尾巴与之前观察到的被认为是由撞击产生的小行星尾巴具有一致的形态。因此，DART 受控撞击实验后抛出物的演化为理解作用于被自然撞击破坏的小行星的基本机制提供了一个框架。
