On Sept. 26, 2022, NASA’s Double Asteroid Redirection Test (DART) successfully crashed into the harmless asteroid moonlet Dimorphos (the smaller of a binary asteroid, the other is Didymos), shortening its orbit around Didymos by a whopping 32 minutes. DART was traveling at 14,000 mph (22,500 kph), or about 20,533 feet/second, at the point of impact. In a “binary asteroid,” two asteroids are traveling through space together, and the smaller one is orbiting the bigger one.
On Dec. 15, NASA scientists gave a briefing on the latest data at a session of the American Geophysical Union’s 2022 fall meeting (Dec. 12-16) in Chicago. (https://www.nasa.gov/feature/nasa-press-events-at-2022-fall-agu-meeting )
The latest findings suggest that the huge amount of ejecta material spewed out into space after impact created an extra push against the asteroid, much like letting air out of a balloon to propel it around a room. The estimate of the amount of material was in the range of 2 million pounds, enough to fill around six or seven rail cars, said NASA (more likely around 9 equivalent in coal cars). The length of the debris plume was estimated to be 18,600 miles (30,000 km) long. Andy Rivkin, DART investigation team leader, reported that this could still be on the low end of the scale; the true figure could possibly be 10 times higher.
Dimorphos is a rocky, “rubble pile” asteroid; if it had a densely-packed hard rock composition, then the debris cloud would have been smaller, and the impact to push the body off course would have been less.
