NASA will hit a spaceship in an asteroid. Things can get quite chaotic.

Led by Harrison Agrusa of the University of Maryland, the researchers modeled how much DART could change the rotation or rotation of Dimorphos by calculating how the inertia of the impact would change the roll, height and curvature of the asteroid. The results can be dramatic. “It can start to roll over and go into a state of chaos,” says Agrusa. “It really was a big surprise.”

The unexpected spin poses some interesting challenges. This will increase the difficulty of landing the asteroid, which ESA hopes to test with two small spacecraft on its mission Hera. In addition, it could make future attempts to deflect an asteroid associated with Earth more complex, as any rotation could affect the asteroid’s path through space.

When DART collides with Dimorphos, the impact energy will be comparable to three tons of explosive TNT sending thousands of pieces of debris spewing into space. Statler describes it as a golf cart that travels at 15,000 miles per hour and crashes on the side of a football stadium. The force of the blow will not cause immediate changes in Dimorphos’ rotation, but within days things will start to change, according to Agrusa and his team.

Soon Dimorphos will start to shake very slightly. This oscillation will grow and grow, as the inertia of the impact throws the rotation of Dimorphos out of balance, without friction in the vacuum of space to slow it down. Dimorphos can begin to rotate in one way or another. It can begin to rotate along its long axis, like baking. For an observer of Didymus looking at the sky, this seemingly calm satellite will take on a new shape – it will begin to swing wildly back and forth, and its hidden sides will now appear.

Within weeks, Dimorphos can rotate so much that it enters a chaotic state of overturning, where it rotates uncontrollably around its axes. In more extreme scenarios, the tidal lock with Didymos could break completely and Dimorphos could start rolling “upside down,” says Agrusa.

What exactly will happen will depend on several things. The shape of Dimorphos will play an important role – if it is more elongated rather than spherical, it will rotate more chaotically. Radar observations so far suggest that it has been extended, but we will not find out until hours before DART strikes when it receives its first views of its small target.