Dart Could Save the Earth from Something Inevitable

 Here is a really big deal.  Such hits are to be expected, catastrophic, and we can now often divert them.

NASA: DART Mission Proves Kinetic Impact Can Save Earth From Incoming Asteroids

By Ryan Whitwam on March 3, 2023 in Extremetech

NASA’s DART mission was a smashing success. The Double Asteroid Redirection Test ended last year with the spacecraft colliding with an asteroid known as Dimorphos. NASA announced in the following weeks that DART had altered the asteroid’s trajectory, and now we have four peer-reviewed papers that explore just how successful the mission was. The news is good — NASA has confirmed that DART validates kinetic impact as a viable way to deflect dangerous asteroids.

DART launched in late 2021 aboard a SpaceX Falcon 9 rocket and is making its way to the Didymos-Dimorphos pair. Didymos is the larger of the two, with a diameter of about 2,500 feet (765 meters), and the smaller Dimorphos (492 feet or 150 meters) orbits it. This arrangement made Dimorphos an ideal target for the impact test as it orbited Didymos every 11.9 hours. Well, it used to — the DART impact caused a dramatic shift in the asteroid’s orbit.

Scientists are working to reconstruct the impact to evaluate DART’s autonomous targeting ability. The authors of this study concluded that a DART-like mission to redirect a dangerous asteroid could theoretically do so without an advanced reconnaissance flight. However, such a preliminary mission would improve the chances of success. The authors further suggest that a redirect could be successful with several years of warning, but several decades would be better.

Another of the four studies confirmed via two different measurement techniques that Dimorphos’ orbit shifted by 33 minutes. NASA had expected the impact to push the asteroid by at least seven minutes, but the recoil effect of ejecta blasted off the surface had a greater effect than predicted. “DART needed to demonstrate that an asteroid could be targeted during a high-speed encounter and that the target’s orbit could be changed. DART has successfully done both,” say the authors.

A separate study looked at the momentum transfer from the impact. The researchers found that DART instantly altered Dimorphos’ orbit, slowing it by 2.7 millimeters per second. The momentum change was amplified by a factor of 2.2 to 4.9, showing the ejecta recoil imparted more energy than the DART spacecraft alone. A future ESA mission will look closer at the impact site, but that won’t happen for several years. The final study discusses what we can learn from DART beyond the planetary defense angle. Dimorphos it’s now an “active asteroid” surrounded by a cloud of dust. The authors say analysis of this comet-like tail could help us learn more about the natural processes at work on asteroids.