Back in September, NASA deliberately crashed a spacecraft into an asteroid to test a potential planetary defense technique. To mark the publication of four new scientific papers that confirm the method works, NASA has now released a video of the impact captured by the Hubble Space Telescope.
NASA and other organizations are building a catalog of asteroids zipping around our neck of the solar system, so that we have as much warning as possible if one were to ever be found on a collision course with Earth. In such an event, we could potentially mount a defensive strike to nudge it away from our home planet, preventing a large-scale or even global catastrophe.
Double Asteroid Redirection Test (DART) was a practice run of just such a strategy. To test whether the orbit of an asteroid could be altered, NASA slammed a probe into a small space rock called Dimorphos, which orbits a larger asteroid known as Didymos. And sure enough, its orbit was quickly seen to have shortened, far more than predicted.
Now the scientific papers discussing the experiment have been published, confirming that the technique is viable, along with further details about what happened. It turns out that Dimorphos’ surface was strewn with far more rocks and boulders than expected, and the impact kicked up a big cloud of dust, which actually gave the asteroid a bit of a boost.
“Pre-impact, we expected the impact to shorten Dimorphos’ orbit by only about 10 minutes,” said Tony Farnham, co-author of the study. “But after the impact, we learned that the orbital period was shortened even more, reducing an ordinarily 12-hour orbit by slightly more than 30 minutes. In other words, the ejected material acted as a jet to push the moon even further out of its original orbit.”
The Hubble Space Telescope also managed to capture a time-lapse video of this material being thrown outwards by the impact, as well as how the cloud evolved over the hours and days afterwards. The video begins 1.3 hours before impact, with a bright spot that contains both Didymos and Dimorphos. The second image shows the system two hours post-impact, with a cone of ejected material visible.
After about 17 hours, the cone begins to morph into a pinwheel shape by the gravitational influence of the larger rock. Next, the debris is swept backwards by the solar wind to form a tail like a comet. Later, this tail strangely splits in half for a few days.
These newly published papers will help inform future missions if we ever need to put this planetary defense plan into action.
The studies were published in the journal Nature [1],[2],[3],[4]. The Hubble video can be seen in the video below.
Sources: NASA, University of Maryland
