Interstellar Visitor Lights Red Planet Sky: A Guide to Comet 3I/ATLAS
In October 2025, comet 3I/ATLAS, an interstellar visitor, made its closest approach to Mars. The European Space Agency’s (ESA) Mars orbiters, the ExoMars Trace Gas Orbiter (TGO) and Mars Express, were strategically positioned to observe this object. This event marks only the third time an interstellar comet has been observed, following 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019, providing scientists with an opportunity to study materials originating from outside our solar system. The observations offer insights into the composition and behavior of these cosmic wanderers, potentially shedding light on the formation of planetary systems beyond our own.
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Official guidance: NIH — official guidance for Complete interstellar visitor lights Red Planet sky Guide
Observing Comet 3I/ATLAS from Mars Orbit
ESA’s ExoMars Trace Gas Orbiter (TGO) played a crucial role in capturing images of comet 3I/ATLAS. On October 3, 2025, the TGO, equipped with its Colour and Stereo Surface Imaging System (CaSSIS), observed the comet from a distance of approximately 30 million kilometers. The CaSSIS instrument, typically used for photographing the Martian surface, successfully detected the comet’s coma, a cloud of gas and dust surrounding the comet’s nucleus. This was a challenging task, as the comet was significantly fainter than the instrument’s usual targets. The TGO’s ability to take longer exposure images, up to five seconds, proved essential for capturing the faint light emitted by the comet.
The Mars Express spacecraft also attempted to observe comet 3I/ATLAS. However, due to its shorter maximum exposure time of 0.5 seconds, detecting the comet proved more difficult. Scientists are currently processing the data from both orbiters, combining multiple Mars Express images to enhance the signal and improve the chances of detecting the comet. The combined efforts of both missions highlight the importance of leveraging different observational capabilities to maximize scientific return during rare astronomical events.
The Coma and Composition of 3I/ATLAS
The images captured by ExoMars TGO revealed the presence of a coma surrounding the nucleus of comet 3I/ATLAS. The coma, which stretches several thousand kilometers across, forms as sunlight heats the comet, causing it to release gas and dust. While the CaSSIS instrument could not resolve the nucleus itself, it successfully detected the coma’s faint glow. The brightness of the coma fades rapidly with distance from the nucleus, making it challenging to measure its full extent. Scientists are interested in analyzing the coma’s composition to understand the materials that make up the comet.
Researchers also attempted to study the comet’s light spectrum using spectrometers on both Mars Express and ExoMars TGO. These instruments aim to identify the chemical composition of the coma and tail. It remains uncertain whether the coma and tail were bright enough to allow for a definitive analysis. However, ongoing analysis of the data collected by these instruments may provide insights into the comet’s origin and the conditions in the interstellar space from which it originated. The study of cometary composition can provide clues about the building blocks of planetary systems and the distribution of elements in the galaxy.
Implications and Future Missions
The observation of comet 3I/ATLAS near Mars offers an opportunity to study an object from outside our solar system. Interstellar comets are valuable because they carry clues about the formation of worlds beyond our own. Unlike objects within our solar system, which share a common origin, interstellar comets are outsiders, providing a glimpse into the diversity of materials and processes occurring in other planetary systems. Studying these objects can help us understand the prevalence of different elements and molecules in the galaxy, as well as the conditions under which planetary systems form.
This event also foreshadows future missions like the Comet Interceptor, designed to chase such visitors. Comet Interceptor, an ESA mission, is designed to rendezvous with a long-period comet entering the inner solar system for the first time. This mission will provide close-up observations of a comet, helping scientists understand the composition and structure of these icy bodies. The data collected from observations of 3I/ATLAS will help inform the planning and execution of future missions aimed at studying comets and other small bodies in our solar system and beyond.
In the coming weeks and months, researchers will continue to analyze the data collected by the Mars orbiters to learn more about comet 3I/ATLAS. This includes studying the comet’s trajectory, composition, and how it changes as it approaches the Sun. The observations of 3I/ATLAS highlight the importance of having versatile and capable spacecraft in place to respond to unexpected events and maximize scientific discovery.
Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional before making health decisions.
Sources: Information based on credible sources and industry analysis.
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