When a spacecraft collided with an asteroid last month, it pushed the spacecraft closer to its partner and accelerated its orbit by around 32 minutes. It’s a tremendous step forward in the subject of planetary defence; it proves that humans may be able to dramatically alter the route of a potentially harmful asteroid — particularly if we have advance information that one is on its way.
On September 26th, observatories on Earth and in space were monitoring the event when the Double Asteroid Redirection Test (DART) mission sent a spacecraft smashing onto its surface. Now, preliminary results from those observatories reveal that DART accomplished its mission. Before the collision, the asteroid Dimorphos orbited its considerably bigger companion asteroid, Didymos, for around 11 hours and 55 minutes. The same journey takes now 11 hours and 23 minutes.
Shaving a half-hour off an asteroid’s orbit is a huge accomplishment for the project, which would have considered even a 73-second difference a success. Researchers believe that one of the causes of the large shift in orbit is that the hit displaced masses of material, resulting in a dramatic-looking cloud of debris. According to NASA, this “recoil” provided the collision an additional kick.
There is still a lot about the effect that scientists will need time to find out. Many more sightings will be analysed to answer queries such, “Is the orbit changing shape?” Is Dimorphos swaying? How much debris was ejected from the asteroid when we collided with it at 14,000 miles per hour?
Once they have that knowledge, the modelling will intensify; they will take the data from the observatories and put it through physics simulations again until they have a solid picture of what occurred. As a result, when the European Space Agency’s Hera spacecraft arrives to the asteroid system in a few years, experts will have a decent notion of what to expect.
All of this is critical information for any future expedition to reroute an asteroid coming toward our planet – the fundamental tenet of planetary defence. Dimorphos and Didymos did not represent a danger to Earth, but experts remain on the alert for additional potentially hazardous asteroids and near-Earth objects.
As exciting as these early DART mission discoveries are, understanding how to move an asteroid is simply one component of any future attempts to shield our planet from space debris. The far greater difficulty is understanding what threats exist and being aware of them as soon as feasible.
A comparable “little shove” to a potentially dangerous asteroid may be sufficient to keep it off of Earth’s course, but time is critical.