NASA asteroid mission could completely deform small moonlet, simulation suggests

NASA’s Double Asteroid Redirection Test (DART) impactor can severely deform the small asteroid it will collide with, a new simulation suggests. It was earlier thought that the DART impactor would leave behind a crater.

The DART impactor is an ambitious mission to test the viability of using a kinetic impactor to deflect an asteroid heading toward Earth. (In this case, kinetic impactor means slamming a spacecraft into the rock.) NASA launched DART aboard a SpaceX Falcon 9 rocket in November and will arrive at its target, the near-Earth asteroid Didymos and its moonlet, Dimorphos, in September.

The study was published on June 1 in The Planetary Science Journal.

DART will hit Dimorphos at 14,760 miles/hour (23,760 km/hour). Mission scientists hope the impact would cause the moonlet’s orbital speed to change by a fraction of a millimetre a second, enough to alter its orbit around the larger asteroid.

While Didymos and Dimorphos are no threat to Earth, they are perfect candidates to test the kinetic impactor concept so that NASA would have a viable option for planetary defence if an asteroid was discovered on a collision course in the future. This is the US space agency’s first dedicated planetary defence mission. The last asteroid impact on Earth occurred 66 million years ago, likely causing the extinction of dinosaurs.

In the simulation, conducted by University of Bern and the National Centre of Competence in Research Planets scientists, the researchers created a new modelling approach to account for the shockwaves and the cratering process that would follow the DART impact. Unlike previous simulations, the model took into account that Dimorphos might not have a solid core, but rather a fragmented, loosely-packed one.

This model suggests that the DART mission could eject more material from Dimorphos than previously thought and potentially alter its course much more strongly.

“Contrary to what one might imagine when picturing an asteroid, direct evidence from space missions like the Japanese space agency’s (JAXA) Hayabusa2 probe demonstrate that asteroid can have a very loose internal structure — similar to a pile of rubble — that is held together by gravitational interactions and small cohesive forces,” said lead author Sabina Raducan, a postdoctoral researcher at the University of Bern.

“This could drastically change the outcome the collision of DART and Dimorphos.”