Five studies confirm the human ability to deflect asteroids

Illustration of NASA's DART spacecraft and the Italian Space Agency's (ASI) LICIACube prior to impact in the Didymos binary system. / NASA/Johns Hopkins APL/Steve Gribben

Science | Space

The articles, published in 'Nature', review what happened after the collision of the DART probe against the Dimorphic moon and shed light on the effectiveness of this planetary defense system

Elena Martin Lopez

It was not a threat to Earth, but on September 26, 2022 NASA's DART (Double Asteroid Redirection Test) mission crashed a spacecraft into Dimorpho, the moon of the asteroid Didymos, to test the human ability to modify the trajectory of these celestial objects, in case in the future it is discovered that one of them is advancing dangerously towards our planet.

The goal was to demonstrate the effectiveness and feasibility of kinetic impact as a potential asteroid deflection method, and the mission was successful. The observations of how it happened and its effects are published this Wednesday in five articles in the journal 'Nature'.

A first study has compared the difference in the orbital period of Dimorph around Didymos before and after the DART impact. To measure this change, they have used two different methods. Both techniques suggest that the asteroid's orbital period around its moon was reduced by about 33 minutes. "The new orbital period causes Dimorph to complete an additional orbit every 9.8 days," the researchers explain in their paper. "The DART probe was intended to serve as a means of testing the kinetic impact technique (or dart test) and to demonstrate both that an asteroid could be hit during a high-speed encounter and that the orbit of the impacted object could be changed, and He has done both successfully," they add.

between two rocks

In a second investigation, the impact of the DART spacecraft on Dimorph is reconstructed. For example, how its different mechanisms worked, such as the SMART navigation system, which helped the probe to position itself in the correct direction for impact; or the DRACO camera, which made it possible to see the crash, live, from Earth. In addition, the morphology of the asteroid is described, oval in shape, with a diameter of 151 meters and a stony surface; as well as the location and nature of the point of impact, which occurred between two rocks. The results will allow for more precise planning of future missions and could help predict the effects of the collision with more certainty.

In the opinion of the authors of this study, "the successful impact of the DART spacecraft with the Dimorph asteroid, and the resulting change in the latter's orbit, demonstrate that kinetic shock technology is a viable technique to potentially defend Earth." if necessary."

ejected dust

The third paper reports Hubble Space Telescope (HST) observations from 15 minutes to 18.5 days after the DART impact, and the velocity and evolution of the dust ejected after the impact. "DART, as a controlled planetary-scale impact experiment, provides a detailed characterization of the target, the morphology of the ejected dust and the evolution of the latter, so it will be the model on which future asteroid studies will be based that show dust tails caused by natural impacts”, affirm the scientists of this research.

In the fourth study, the amount of momentum that was transferred from the spacecraft to the asteroid at the moment of impact is determined, noting that Dimorph's orbital velocity was reduced after the crash.

Observations of Dimorphs before, during and after the impact, carried out by a global network of citizen science telescopes, have been collected in a fifth article. In it, the researchers have calculated the mass and energy of the ejected dust, as well as its evolution over time, which will help to better understand the results of impact missions.