Without this collision, these two small objects would have remained forever anonymous. Instead scientists gained a serendipitous insight into the destructibility of asteroids, which could help defend Earth against future asteroid hazards. After all, “the best way to see how hard something is, is to break it,” said Olivier Hainaut, an astronomer at the European Southern Observatory and lead author of the study published earlier this year in Astronomy & Astrophysics.

Astronomers first discovered P/2016 G1 with the Pan-Starrs1 telescope in Hawaii in April 2016. Backtracking through archived images, astronomers realized that it had first been visible the previous month as a centralized collection of rocky clumps: the fractured, rubbly remnants of the asteroid, surrounded by a fine dust cloud, most likely the immediate debris jettisoned by the impact.

Over the ensuing weeks, an expanding ring of debris could also be seen emerging from the object. Computer simulations revealed this to be the beginning of a cone of uplifted rubble, a signature feature of an impact event.

After the initial debris cloud was created, the cratering process lost energy and subsequent streams of debris were more slowly excavated from the asteroid’s new scar. On Earth, this ring of debris would land around the crater. But on a tiny asteroid with little gravity, this debris ring simply flew into space, expanding as it went.

There is no clear date when the asteroid disappeared. Documenting the vanishing of P/2016 G1 was like tracking a drop of milk in your coffee, Dr. Hainaut said: Parts spread out and faded away individually. In any case, as of December 2018, the asteroid could no longer be seen.