Led by Harrison Agrusa of the University of Maryland, the researchers modeled how Dart could change the spin or rotation of the dimorphos by calculating how the speed of impact would change the asteroid’s roll, pitch, and yaw. The results can be dramatic. “It could start to sink and enter chaos,” says Agrasa. “It was a really big surprise.”
Unexpected spinning creates some interesting challenges. This will add to the difficulty of landing on the asteroid, which the ESA hopes to try with two smaller spacecraft on its Hera mission. It may try to further complicate the Earth’s asteroid in the future, as any rotation could affect an asteroid’s path through space.
When the dart hits Demorphos, the force of impact will be comparable to a three-ton TNT explosion, sending thousands of pieces of debris into space. Statler describes it as a golf cart that travels at a speed of 15,000 miles per hour next to a football stadium. According to Agrasa and his team, the impact of the impact will not bring about an immediate change in Dimorphos ’spin, but within a few days things will start to change.
Soon, the dimorphs will begin to shake very little. This push will increase and increase as the motion from the impact unbalances the rotation of the dimorphos, slowing it down without rubbing into the vacuum of space. Dimorphos can begin to rotate one way or another. It can begin to rotate along its long axis, like a rotisserie. Looking up at the sky to an observer from Didimos, this seemingly naive satellite will take on a new form as the wild begins to sway backwards, its previously hidden aspects now becoming visible.
Within a few weeks, the dimorphs can rotate so much that it falls into a chaotic state where it rotates uncontrollably around its axis. In more extreme situations the tidal lock with Didimos could be completely broken and Demorphos could start to “head over heels”, Agrusa says.
Exactly what will happen will depend on a few things. The shape of the dimorphos will play an important role – if it is elongated instead of round, it will rotate more chaotically. Radar observations so far suggest prolonging it, but we may not know just hours before DART hits, when it gets the first impression of its small target.