NASA probe collides with asteroid – there may not be an impact crater

NASA's DART probe successfully diverted an asteroid. Now a new study reveals surprising findings about the impact crater.

Munich – In the fall of 2022, NASA conducted a planetary defense test with its DART space probe by targeting the asteroid Dimorphos and allowing the probe to impact. The question was whether an asteroid heading toward Earth could be blown off course by a “kinetic impact.” Answer: Yes. Dimorphos' orbit around the larger asteroid Dynamos was shortened by 33 minutes after the collision.

The European Space Agency (ESA) now plans to launch the Hera space probe in October 2024, which will reach the pair of asteroids in 2026 and examine the crater on Dimorphos created by Dart. One recently in Nature astronomy Published study However, this indicates that this crater may not even exist.

Researchers simulate the impact of a NASA probe on an asteroid

A team of scientists led by Sabina Raducan from the University of Bern used the Bern SPH software system to simulate the collision of the NASA spacecraft with the asteroid. The system turns colliding objects into millions of particles whose behavior can be affected by different variables. The team used all known values, such as the mass of DART, the approximate shape of the asteroid, and the size of the cloud of material resulting from the collision. The unknown variables were constantly changing.

“This is a computationally intensive process with each simulation taking about a week and a half,” Raducan explains. “In total, we ran about 250 simulations, replicating the first two hours after the collision.

Does the asteroid Demorphos have an impact crater at all?

“We then checked which of the simulation results closely matched the observed reality,” the researcher adds. “The results indicate that the Dimorphos asteroid is a relatively weak asteroid, held together by the asteroid's very weak gravity rather than by a cohesive force.” The connection between atoms and molecules within a material, which ensures its cohesion.

The team also focused on the crater that the Hera probe will study in the future. “A crater event is usually terminated either by gravity or by the force of the cratered material,” explains study co-author Martin Goetzi. On Earth, high gravity creates a “typical nozzle cone angle” of about 90 degrees. However, in 'Dimorphos', the ejection cone had an angle of up to 160 degrees. “The crater continued to expand because the gravity and material cohesion were so low,” Goetzi describes.

Researcher: The asteroid became a “completely different object” after the collision

Raducan goes further and says: “It is possible that the crater grew to cover the entire body, and eventually reshaped the entire dimorphos.” As a result, Hera is unlikely to find any craters left by DART. “What you'll discover instead is a completely different body.” According to the researcher, the simulations indicate that the original shape of “Dimorphos” has become faint on one side. “If you imagine Dimorphos started out looking like an M&M, now it looks like someone took a bite of it,” she explained.

Even if there is no impact crater, the Hera spacecraft will have a lot to analyze when it visits Dimorphos. Despite already completed missions such as OSIRIS-REx or Hayabusa-2, their visit to the asteroid is one of the few asteroid missions ever. (unpaid bill)

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