Comet 3I/ATLAS shows activity in Juice navigation camera teaser
During November 2025, ESA’s Jupiter Icy Moons Explorer (Juice) used five of its science instruments to observe 3I/ATLAS. The instruments collected information about how the comet is behaving and what it is made of.
Grainy space image, with white dots on a dark background. At the centre of the image is a larger, bright white blob with a faint white line stretching towards the top of the frame.
In addition, Juice snapped the comet with its onboard Navigation Camera (NavCam), designed not as a high-resolution science camera, but to help Juice navigate Jupiter’s icy moons following arrival in 2031.
Though the data from the science instruments won’t arrive on Earth until February 2026, our Juice team couldn’t wait that long. They decided to try downloading just a quarter of a single NavCam image to see what was in store for them. The very clearly visible comet, surrounded by signs of activity, surprised them.
Not only do we clearly see the glowing halo of gas surrounding the comet known as its coma, we also see a hint of two tails. The comet’s ‘plasma tail’ – made up of electrically charged gas, stretches out towards the top of the frame. We may also be able to see a fainter ‘dust tail’ – made up of tiny solid particles – stretching to the lower left of the frame. More on the structure of a comet.
The image was taken on 2 November 2025, during Juice’s first slot for observing 3I/ATLAS. It was two days before Juice’s closest approach to the comet, which occurred on 4 November at a distance of about 66 million km.
We expect to receive the data from the five scientific instruments switched on during the observations – JANUS, MAJIS, UVS, SWI and PEP – on 18 and 20 February 2026. The delay is because Juice is currently using its main high-gain antenna as a heat shield to protect it from the Sun, leaving its smaller medium-gain antenna to send data back to Earth at a much lower rate.
Though Juice was further from 3I/ATLAS than our Mars orbiters were back in October, it observed 3I/ATLAS just after the comet’s closest approach to the Sun, meaning that it was in a more active state. We expect to see clearer signs of this activity in the data from the science instruments. This includes not only images from JANUS – Juice’s high-resolution optical camera – but also spectrometry data from MAJIS and UVS, composition data from SWI, and particle data from PEP.
For the latest updates and FAQs related to comet 3I/ATLAS, see esa.int/3IATLAS.
Click here to download an annotated version of the image.