What Will Hera Learn From NASA’s Asteroid Test?
What Will Hera Learn From NASA’s Asteroid Test?
NASA's DART mission hit the asteroid moon Dimorphos in September 2022. The collision was intentional and was designed as a planetary-defense test. After the impact, Dimorphos completed its orbit around Didymos faster than before. That showed that a spacecraft impact can measurably change the motion of a small asteroid body. ESA's Hera mission will study the same system from close range. Its job is to explain the physical details behind that successful change in orbit.
Why mass is one of the biggest questions
Scientists know how much DART changed the orbit, but they still need a better measurement of Dimorphos's mass. Mass matters because it affects how difficult an object is to move. Hera can study the gravity and motion of the asteroid system to improve that estimate. Once mass is better known, researchers can calculate the transfer of momentum more accurately. That shows how much extra push came from material blasted away during the impact. It also helps researchers compare DART with possible future deflection missions.
The surface can show how the asteroid responded
DART struck Dimorphos at high speed and threw material into space. Hera will map the surface and impact area in much greater detail. Researchers want to know whether a clear crater formed. They also want to know whether the whole small moon changed shape. A loose asteroid can move and deform in ways that a solid rock would not. The surface record can therefore reveal important clues about the material inside Dimorphos.
The inside may be even more important
Small asteroids are often described as rubble piles, but that phrase can cover many different structures. Some may be tightly packed, while others can contain large empty spaces. Large boulders can also be mixed with much smaller material. Juventas, one of Hera's CubeSats, carries radar designed to probe below the surface. That can give researchers a better picture of the internal structure. Knowing the inside helps explain why the outside reacted the way it did.
Why one successful impact is not enough
DART proved that an impact can work on one real asteroid system. That does not mean every asteroid would respond in exactly the same way. A larger, denser or faster-spinning object could behave differently. An asteroid made of loose material may also absorb and release energy differently from a solid body. Planetary defense therefore needs both real tests and computer models. Hera gives scientists the detailed measurements needed to improve those models.
What Hera could change for future missions
Future asteroid missions may need to decide how hard, where and when to strike a dangerous object. Those decisions depend on how well scientists understand the target. Hera's measurements can improve estimates of impact efficiency. They can also help researchers understand which uncertainties matter most before a mission launches. The goal is not to create one universal formula for every asteroid. Paleon presents Hera as a follow-up science mission that improves our understanding, not as proof that every asteroid threat is now solved.