Recent observations from the ExoMars and Mars Express orbiters have captured significant data regarding comet 3I/ATLAS. This comet, detected on July 1, 2025, represents the third confirmed interstellar comet observed to date, following 1I/ʻOumuamua and 2I/Borisov.
Close Encounter with Comet 3I/ATLAS
On October 3, 2025, comet 3I/ATLAS approached its closest point to Mars. At that time, it was approximately 30 million kilometers away from the two orbiters. Both the ExoMars Trace Gas Orbiter (TGO) and Mars Express utilized their specialized cameras to capture images of this distant celestial object.
Imaging Capabilities
The ExoMars TGO employed the Colour and Stereo Surface Imaging System (CaSSIS) to create a series of images. The comet appeared as a blurred white dot, which is the central part of its icy-rocky nucleus and surrounding coma. However, due to the vast distance, distinguishing finer details was challenging.
- The nucleus of the comet is approximately one kilometer wide.
- The coma extends several thousand kilometers, formed by gas and dust released as the comet nears the Sun.
- As the Sun’s heat activates the comet, it generates a tail that can potentially stretch millions of kilometers.
Nick Thomas, the Principal Investigator of CaSSIS, noted that this observation posed significant challenges. He remarked that 3I/ATLAS is notably fainter than typical targets, making imaging complex.
Data Collection and Future Analysis
While the ExoMars TGO successfully captured the comet, Mars Express had limitations due to shorter exposure times. This resulted in limited visibility of 3I/ATLAS in its images. However, scientists plan to analyze data over the following weeks and months to gather more insights about the comet’s composition and behavior as it approaches the Sun.
Colin Wilson from ESA expressed excitement over the opportunity to study this unexpected event. He stated that the Mars orbiters continue to provide valuable insights into Martian science and at the same time, contribute to the understanding of celestial phenomena.
Comet 3I/ATLAS’s Unique Characteristics
Comet 3I/ATLAS presents a rare opportunity for scientists. As an interstellar object, it offers clues about the formation of worlds outside of our solar system. Astronomers believe that this comet might be over three billion years older than our 4.6 billion-year-old Solar System.
Upcoming Observations and Future Missions
Next month, the Jupiter Icy Moons Explorer (Juice) will observe 3I/ATLAS shortly after its closest approach to the Sun, potentially in a more active state. However, data from these observations will not be available until February 2026.
Looking ahead, ESA is preparing for the Comet Interceptor mission set to launch in 2029. This mission aims to target pristine comets from the Oort Cloud or other interstellar objects like 3I/ATLAS. Michael Kueppers, the project scientist for the Comet Interceptor, emphasized the mission’s potential to improve our understanding of interstellar objects and their diverse characteristics.
Conclusion
The collaborative efforts of the ExoMars and Mars Express missions underscore the significance of ongoing research into celestial phenomena. As observations of comet 3I/ATLAS continue, they will undoubtedly enhance our understanding of the cosmos and our place within it.
