Media release

From: Springer Nature

Astronomy: Assessing the impact of the DART mission

Observations of NASA’s Double Asteroid Redirection Test (DART) on the moon of a near-Earth asteroid are reported in five papers published in Nature this week. Some of these observations come from citizen science telescopes around the world. Understanding how the impact of the DART spacecraft changed the orbit of the moon sheds light on how this approach might be able to provide a defence system against potential collisions of astronomical objects with Earth.

The DART mission ran a spacecraft into Dimorphos, the moon of near-Earth asteroid (65803) Didymos, on 26 September 2022. The aim of the collision was to change the orbit of the moon, testing a potential method of asteroid deflection. Estimations of the change in momentum of the moon and a description of how momentum was transferred from the spacecraft to the moon are revealed in five papers published in Nature.

Cristina Thomas and colleagues determine the change in the orbital period of Dimorphos around Didymos after the DART impact. Two independent approaches to measure this change suggest that the orbital period was reduced by around 33 minutes. Ronald Terik Daly and colleagues reconstruct the impact of the DART spacecraft on Dimorphos, which may help with the planning of future missions and could help to predict outcomes with more certainty. They also describe the location and nature of the impact site, noting that it was between two boulders, one of which was grazed by the spacecraft as it made contact with the moon. Jian-Yang Li and colleagues report Hubble Space Telescope observations of the ejecta plume (debris created by the impact), the speed and evolution of which may explain the momentum change caused by the impact. Andrew Cheng and colleagues note that the orbital velocity of Dimorphos reduced after the impact. They propose that the momentum transfer from the spacecraft to the moon was enhanced by recoil from ejecta streams produced by the impact. Observations of Dimorphos before, during and after the impact — made by a global network of citizen science telescopes (including three on Réunion Island and one in Nairobi, Kenya, that captured the moment of impact) — are reported by Ariel Graykowski and colleagues. They estimate the mass and the energy of the ejected dust, and its evolution over time, which may help us to understand the outcomes of impact missions.