When NASA’s DART mission smashed into a small asteroid, they were able to get a very accurate idea of the spacecraft’s weight and speed. Combining this with estimates of the motion and mass of our target asteroid, Dimorphus, we can easily calculate to estimate how much momentum is lost by the asteroid and what that means for its orbit. can. This calculation should ultimately shorten the orbit of Dimorphus by about 7 minutes.
Instead, the trajectory was shortened by 30 minutes, more than four times that amount.
Today’s issue of Nature includes five articles that collectively reconstruct the impact and its aftermath to explain how the DART crash had a far-reaching impact. And in the process, the paper shows that impactors like DART could be a viable means of defending Earth from small asteroids.
feeling defensive
It’s easy to forget the role software played in DART’s success. We didn’t send anything to the Didymos/Dimorphos binary system to scout the location first. Instead, NASA launched her DART with one camera and some navigation software that has a rough idea of what to expect. When the software took over, the camera couldn’t even resolve the small Dimorphus, instead keeping DART moving towards Didymos for about 25 minutes until a small asteroid became visible.
Dimorphus has a diameter of about 150 meters on its longest axis, but we know where DART hit it within 68 centimeters. This location is found to be close to the ideal location to maximize momentum transfer from the spacecraft to the asteroid. An on-board camera also provided detailed images of the crash site up to seconds before it was destroyed. Combined with knowledge of the spacecraft’s orientation, this allows for a very detailed description of the impact.
The spacecraft approached the asteroid with the solar array tilted slightly toward the surface. The leading edge of the +Y solar array touched the surface of boulder 1 and this solar array directly impacted boulder 1. Shortly thereafter, the -Y solar array grazes Boulder 2 and the leading edge of the -Y array touches the surface. Near the base of Boulder 2 in the downrange direction. Finally, the spacecraft bus collided between rocks 1 and 2.
This indicates that we now have the technology necessary to intercept small asteroids without the need for sophisticated reconnaissance beforehand. And, as we’ve known for some time, spacecraft can significantly alter asteroid trajectories. Therefore, from a planetary defense perspective, DART was the primary validation.
Most of the remaining new information focuses on why the orbital shift was much larger than simple calculations suggest.
