Introduction: A Visitor from Beyond the Solar System
Two Mars-orbiting spacecraft have offered the closest view yet of the mysterious interstellar visitor 3I/ATLAS. In a concerted effort, the European Space Agency (ESA) and NASA’s fleet of robotic explorers captured fresh imagery as the comet passed near the Red Planet on its months-long journey through the inner solar system. This unprecedented look helps scientists study a body that originated outside our solar neighborhood, potentially billion-year-old material from a distant star.
What the New Images Show
During its flyby, the comet came within roughly 30 million kilometers (about 18.6 million miles) of Mars. ESA’s ExoMars Trace Gas Orbiter (TGO) delivered the clearest views, which ESA later assembled into an animated sequence. In these frames, the comet appears as a fuzzy, bright dot moving closer to the center of the image before drifting away at high speed—estimated around 210,000 kilometers per hour (130,000 mph).
The near resolution isn’t enough to resolve a visible tail, which is common for such a distant, faint object. Mars Express, another ESA spacecraft, could not capture the comet due to its greater distance and the characteristic faintness of the target from that vantage point. Nevertheless, the TGO’s data provide valuable insight into the comet’s behavior in the inner solar system.
Understanding 3I/ATLAS: What We Know So Far
3I/ATLAS is the third confirmed interstellar object detected passing through our solar system, following 1I/‘Oumuamua and 2I/Borisov. Current estimates suggest a size between 3 and 7 miles (5 to 11 kilometers) and an orbit that confirms its interstellar origin. Its velocity and trajectory imply it has traversed the galaxy for billions of years, likely sailing through interstellar space long before the Sun formed.
As a comet, 3I/ATLAS carries volatile ices that sublimate as it approaches the Sun. This sublimation creates a coma, a glowing cloud around the nucleus, and sometimes a tail shaped by solar wind. In these Mars-era observations, the coma may begin to brighten as the object moves closer to the Sun, even if the tail remains faint or unseen at Mars’ distance.
The Role of ExoMars TGO and Mars Express
The ExoMars Trace Gas Orbiter is designed to study Mars’ atmosphere and surface, equipped to monitor fine details from a few hundred miles away. While its instruments aren’t optimized for tracking distant, fast-moving targets like 3I/ATLAS, it provided the best available imagery from Mars’ orbit during the recent flyby. In contrast, the more distant Mars Express had limited viewing capability for this particular encounter, underscoring the challenges of capturing interstellar visitors with current equipment.
What Comes Next for 3I/ATLAS Observations?
ESA officials expect the comet’s coma and possibly its tail to brighten as it approaches perihelion on Oct. 30, offering potential for brighter imagery in future observations. Ground-based observatories and other space telescopes will continue tracking 3I/ATLAS, providing complementary data on its size, composition, and trajectory as it travels by the Sun and swings outward again. While the U.S. government shutdown momentarily limited some data releases, independent space science outlets continue to monitor and report on the latest developments.
Why Studying an Interstellar Visitor Matters
Interstellar objects like 3I/ATLAS are natural time capsules from other star systems. By analyzing its composition, activity, and structure, scientists can gain clues about materials and processes that existed elsewhere in the galaxy long before the solar system formed. Each observation helps refine models of how comets form and evolve across the cosmos, and it offers a rare chance to compare extraterrestrial materials with those found in our own solar neighborhood.
What to Expect for the December Sky and Beyond
After rounding the Sun, 3I/ATLAS will reappear for Earth-based telescopes in December and continue on its interstellar voyage. Its next notable close approach to major planets will be a pass by Jupiter in March 2026, after which it will drift further into interstellar space. Until then, ESA and partner agencies will sift through the latest data to extract any new clues about this extraordinary interstellar traveler.
