The collision between NASA's Dart probe and the asteroid Dimorphos on Sept. 26, 2022, 11 million km from Earth, was not only the first planetary defence mission ever carried out, but it also provided a unique opportunity to gain new knowledge about asteroids by studying the debris produced during the impact.
Data on the collision gathered by the European Southern Observatory's (Eso) Very Large Telescope (Vlt) in fact became the basis for two subsequent studies.
The first study , led by Cyrielle Opitom of the University of Edinburgh, is published in Astronomy & Astrophysics and followed the evolution of the debris cloud for a month. The researchers found that initially the cloud was bluer than the asteroid because it was formed by very fine particles, while other structures that developed later were redder because they were made of larger material.
The second study , led by Stefano Bagnulo of the Armagh Observatory in Northern Ireland and also featuring Alberto Cellino of the National Institute of Astrophysics (Inaf), and published in Astrophysical Journal Letters, looked at how the impact with Dart changed the asteroid's surface. The data indicate that Dimorphos became brighter immediately after the collision, with two possible explanations: the collision may have exposed pristine material from inside the asteroid that was brighter than the surface; or the resulting cloud of tiny debris was more efficient at reflecting light.
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