Hera mission advances to Didymos as comet 3I/ATLAS intrigues with mysterious acceleration

The international scientific community is following with great interest two distinct cosmic events that converge in importance for planetary defense. On one hand, the Hera mission, from Agência Espacial Europeia (ESA), continues its journey towards the Didymos-Dimorphos asteroid system, scheduled to arrive in December 2026.

The comet, which will pass at a relatively close distance to Terra on December 19, shows accelerations and jets of material that cannot be explained solely by the sublimation of ice under the influence of Sol. Essas observations raise questions about its composition and origin, making it a priority object of study.

Meanwhile, the Hera probe, launched on October 7, 2024, aims to analyze the consequences of the deliberate impact of NASA’s DART mission, which in 2022 successfully altered the orbit of the asteroid Dimorphos. The data collected by Hera will be crucial for validating and refining techniques for deflecting celestial objects that could pose a future threat to our planet.

The mysterious behavior of comet 3I/ATLAS

Observed closely since early 2025, 3I/ATLAS has been a source of surprises for astronomers. Earth- and space-based Telescópios, like Hubble, have recorded irregular brightness peaks and jets of dust and gas that emanate in lateral directions, rather than aligning with the direction of sunlight, as would be expected.

The comet’s measured acceleration significantly exceeds values ​​that could be justified solely by the “rocket” force generated by the melting of its surface. Além Additionally, NASA data revealed the presence of an ultraviolet halo around the object, with features that do not match the patterns of known comets in our solar system, suggesting a unique chemical composition.

The journey of the Hera probe to the Didymos system

The Hera mission represents the European part of an international asteroid assessment collaboration. After its successful launch, the probe entered an interplanetary cruise phase, performing systems checks and minor course corrections to ensure that its trajectory takes it precisely toward the Didymos system.

Arrival in December 2026 will mark the beginning of a detailed investigation phase. Hera will be the first spacecraft to perform an orbital encounter with a binary asteroid system, a class of objects that makes up about 15% of all known asteroids. The mission will not only study Dimorphos, the DART target, but also the larger asteroid, Didymos.

Operations on the system will be complex, requiring high-precision autonomous navigation maneuvers to orbit the two bodies in a low-gravity environment. The control team, located at Alemanha, constantly monitors the health and progress of the probe, preparing for the intense scientific phase ahead.

Assessing the legacy of the DART mission

The main goal of Hera is to transform the large-scale DART experiment into a well-understood and replicable planetary defense technique. The 2022 impact was a monumental success, changing the orbital period of Dimorphos by 33 minutes, much longer than the minimum expected, proving that the kinetic impactor technique works.

Now, Hera will provide the missing data. The probe will map the impact crater left by DART in detail, which will help scientists better understand the momentum transfer of the impact. Essa information is vital for calculating the amount of force needed to deflect asteroids of different sizes and compositions.

Instruments on board will also precisely measure the mass and shape of Dimorphos, determining how the impact altered its internal structure and surface. Imagens captured by the Italian cubesat LICIACube, which accompanied DART, showed a huge ejection of material, and Hera will analyze the remaining debris to understand the mechanics of the collision.

Additionally, two small satellites, or CubeSats, called Juventas and Milani, will be launched by Hera. Eles will perform complementary measurements, including a low-frequency radar to probe the interior of Dimorphos and spectral analyzes of its surface dust. Esses data will provide unprecedented insight into the physics of asteroid impacts.

Cutting-edge technology for space exploration

To meet its ambitious goals, Hera is equipped with a suite of advanced technologies. Seu optical navigation system is one of the most sophisticated ever sent into deep space, allowing the probe to maneuver autonomously within a few meters of its targets. High-resolution Câmeras and a laser altimeter will create detailed 3D maps of the asteroids’ surface.

Onboard spectrometers will analyze the chemical composition of the surface exposed by the DART impact, revealing materials from Dimorphos’s interior that were not previously visible. Esses data is essential to understanding the formation of asteroids and how they respond to external forces. Combining these tools will allow for a complete characterization of the binary system, providing a valuable model for future asteroid studies.

Planetary defense in focus

The simultaneous occurrence of 3I/ATLAS monitoring and the Hera mission highlights science’s dual approach to planetary defense: observing and cataloging natural threats while actively developing and testing methods to mitigate them. Comet 3I/ATLAS, with its trajectory variations without a clear external cause, serves as a powerful reminder that celestial bodies can have unpredictable behaviors. Compreender these anomalies is as crucial as learning to artificially influence the trajectory of an object. The Hera mission, on the other hand, studies exactly how to change the movements of celestial bodies in a controlled way. The results obtained in Dimorphos will not be just theoretical; they will serve as a technical manual, a fundamental reference that will inform the design and strategy of future land protection missions. The close collaboration between ESA and NASA in this global effort demonstrates a unified commitment to protecting the planet by exchanging data in real time to maximize the knowledge gained from both celestial events.

Next steps in monitoring

In the coming months, attention will continue to be divided. Observatórios around the world will maintain continuous coverage of 3I/ATLAS, especially during its closest approach in December. At the same time, the Hera mission teams will carry out the final trajectory corrections and instrument tests, preparing the probe for its arrival and the beginning of its scientific phase at the end of 2026, when the first results will begin to be released.