The European Space Agency’s Hera mission is helping scientists develop a better understanding of asteroids and investigate technologies that could one day help protect Earth from a dangerous space object.

The spacecraft is designed to study the Didymos asteroid system, particularly the smaller asteroid Dimorphos, which was struck by NASA’s Double Asteroid Redirection Test (DART) spacecraft in 2022. That earlier experiment demonstrated that a spacecraft impact could change an asteroid’s orbital motion.

Hera’s scientific investigation will provide detailed measurements of the asteroid system and help researchers understand how effective such an impact could be under different conditions.

A Follow-Up to NASA’s Historic Asteroid Impact

NASA’s DART mission deliberately collided with Dimorphos to test whether a spacecraft could alter an asteroid’s movement. Observations after the impact showed that Dimorphos’s orbital period around its larger companion, Didymos, had changed.

The experiment represented a major step in planetary defence research because it demonstrated a practical method for changing the motion of a small celestial body.

However, the outcome of an impact depends on several factors, including an asteroid’s mass, shape, internal structure and surface characteristics.

Hera is intended to examine these factors more closely, allowing scientists to improve their understanding of the physical processes involved.

Why Scientists Are Studying Dimorphos

Asteroids vary considerably in size, composition and structure. Some may consist of relatively solid rock, while others may be loosely packed collections of fragments held together by gravity.

These differences can strongly influence how an asteroid responds to a high-speed collision.

Hera’s observations are expected to help scientists investigate the structure of Dimorphos, examine the impact site and measure changes associated with the DART experiment.

The findings could help researchers develop more reliable models for predicting the results of future asteroid-deflection missions.

Understanding the Threat From Near-Earth Objects

Near-Earth objects are asteroids and comets whose orbits bring them relatively close to Earth’s orbital neighbourhood. Most pose no immediate danger, but identifying and tracking potentially hazardous objects is an important part of planetary defence.

Scientists use ground-based telescopes and space-based observations to determine the orbits, sizes and characteristics of these objects.

If an asteroid were found to pose a significant future impact risk, early detection would be essential because a deflection mission could require years of planning and preparation.

The effectiveness of any response would depend on the object’s characteristics, the warning time available and the ability to launch a suitable spacecraft.

International Cooperation in Planetary Defence

Hera represents cooperation between the European Space Agency and the wider international planetary-defence community.

NASA’s DART mission and ESA’s follow-up investigation illustrate how separate missions can contribute to a shared scientific objective.

Combining observations from different spacecraft and telescopes can improve the accuracy of asteroid models and help researchers evaluate potential deflection techniques.

International collaboration is particularly valuable because asteroid threats do not respect national boundaries. A major impact could have consequences for the entire planet.

Technology Developed for Future Missions

Hera carries scientific instruments designed to examine the asteroid environment and measure important physical properties. Its mission also involves advanced spacecraft navigation and operations near small celestial bodies.

The spacecraft is accompanied by small CubeSats intended to conduct additional observations and measurements around the asteroid system.

Operating near a small asteroid presents significant engineering challenges because its weak gravity and irregular shape complicate navigation and manoeuvring.

Experience gained during the mission could improve the design of future spacecraft intended to investigate or respond to potentially hazardous objects.

What the Mission Could Mean for Earth

Hera’s scientific results could help answer important questions about how an asteroid responds to an impact and how accurately scientists can predict the outcome of a deflection attempt.

Such knowledge would be valuable if a potentially dangerous asteroid were discovered in the future.

Nevertheless, planetary defence requires more than impact technology. It also depends on discovering hazardous objects early, accurately determining their trajectories and coordinating decisions among countries.

The Road Ahead

The Hera mission forms part of a long-term effort to transform asteroid deflection from a demonstrated experiment into a better-understood planetary defence capability.

By examining the aftermath of the DART impact, ESA aims to provide scientists with information that can improve future mission planning and asteroid-risk assessment.

The research could strengthen humanity’s ability to prepare for rare but potentially serious natural hazards originating in space.