Two probes from the European Space Agency (ESA) captured rare images of the interstellar comet 3I/ATLAS, an object from another star system, during its passage 30 million kilometers from Mars on October 3, 2025. The Mars Express and Trace Gas Orbiter spacecraft recorded the celestial body, appearing as a white dot surrounded by a cloud of gas and dust. The observation, considered a technical feat, was the closest ever made by ESA of such a comet. Collected data may reveal the comet’s chemical composition and origin.
Discovered in July 2025 by the ATLAS project in Chile, the comet is only the third interstellar object identified, following ʻOumuamua (2017) and Borisov (2019). Its trajectory suggests it may be up to 3 billion years older than the Sun.
- Images show the coma, a gas and dust cloud, spanning thousands of kilometers.
- The comet’s tail may become visible in the coming weeks.
- The Juice probe will observe 3I/ATLAS in November, in a more active phase.
Technology adapted for observation
The probes’ cameras, designed for mapping Martian terrain, were adjusted to capture the comet. The CaSSIS instrument on the Trace Gas Orbiter overcame technical challenges by imaging an object up to 100,000 times fainter than typical targets.
The adjustments enabled clear images, comparable to spotting a cellphone on the Moon from Earth. ESA plans to continue monitoring the comet to gather more data on its composition.
Cosmic origin of 3I/ATLAS
The 3I/ATLAS is a relic from another star system, formed around a distant star billions of years ago. Its speed and trajectory confirm it does not belong to our Solar System.
Astronomers believe the comet holds clues about the formation of planetary systems. Analysis of its reflected light may reveal chemical elements in its core.
Preliminary studies suggest 3I/ATLAS consists of ice, dust, and volatile gases.
Its passage near the Sun is expected to intensify particle emissions.
Observation in November
The Juice probe, exploring Jupiter’s icy moons, will make further observations of the comet in November. Despite the greater distance, the comet will be more active, releasing more gas and dust.
The collected data will enhance understanding of interstellar comets’ dynamics.
ESA emphasizes the role of Martian missions in deep-space studies.
The observation showcases the probes’ versatility in responding to unexpected events.
Contribution to science
The 3I/ATLAS sighting underscores the value of space missions in discoveries beyond their primary goals. The images and data pave the way for new analyses of interstellar objects.
ESA hopes the observations will reveal more about the formation and evolution of star systems.
Impact for future missions
The ability to reconfigure equipment for rare events may inspire new strategies for space missions. ESA considers adapting other probes for similar observations in the future.
Technical details of the capture
Capturing 3I/ATLAS required precise camera adjustments. The comet’s low brightness challenged the instruments’ limits, designed for brighter targets. ESA celebrates the achievement as a milestone in space observations.
