This striking image from the science camera on ESA’s Jupiter Icy Moons Explorer (Juice) shows interstellar comet 3I/ATLAS spewing dust and gas. The tiny nucleus of the comet (not visible) is surrounded by a bright halo of gas known as the coma. A long tail stretches away from the comet, and we see hints of rays, jets, streams and filaments.
The inset in the image shows the same data, but processed to highlight the coma structure. The arrows in the top left indicate the direction in which the comet was moving (blue) and the relative direction of the Sun (yellow). While 3I/ATLAS is a visitor from interstellar space, travelling from outside the Solar System, its behaviour is completely in line with that expected from a ‘normal’ comet.
The camera, named JANUS, took this image on 6 November 2025, just seven days after the comet made its closest approach to the Sun. At the time, Juice was about 66 million km away from the comet.
Throughout November, Juice used five of its science instruments to observe 3I/ATLAS – JANUS, MAJIS, SWI, PEP and UVS. Together, they collected information that will reveal how the comet was behaving and what it is made of.
During the months that followed the observations, Juice was on the opposite side of the Sun to Earth. It was using its main high-gain antenna as a heat shield, and its smaller medium-gain antenna to send back data to Earth at a lower rate. This meant that instrument teams had to wait until last week to receive the data; they are now working hard to analyse them.
In total, JANUS took more than 120 images of 3I/ATLAS across a large wavelength range. The instrument team is taking a closer look at all these images to understand what they reveal about the comet.
Meanwhile, the MAJIS and UVS teams are busy studying spectrometry data, those behind SWI are investigating data on the comet’s composition, and the PEP team is digging into particle data. Together with the ESA team working on Juice’s navigation camera, which also photographed 3I/ATLAS, they will all come together in late March to discuss their findings.
Science is slow, but as the instruments teams are now all-too-aware, good things come to those who wait. Stay tuned for an update from us.
For the latest updates and FAQs related to comet 3I/ATLAS, see esa.int/3IATLAS.
JANUS is a multicolour optical camera designed to take detailed, high-resolution photos of Jupiter and its icy moons. It was developed by an industrial consortium led by Leonardo SpA, under the supervision of the Italian Space Agency (ASI) and in collaboration with the Italian National Institute for Astrophysics (INAF), which is responsible for instrument science, the German Aerospace Center (DLR), CSIC-IAA in Granada (Spain) and CEI-Open University in Milton Keynes (UK).
[Image description: A white, glowing egg-shaped object lies in the centre of the black-and-white image, on a dark, starry background. Glowing streaks spread upwards from the object. In the top left, a yellow arrow marked ‘Sun’ points straight down, and a blue arrow marked ‘Velocity’ points towards the 7 o’clock direction. In the bottom left, an inset shows the same object on a lighter grey starry background, filled with ragged-edged, concentric egg shapes gradiented black-to-white.]