NASA and the European Space Agency say its Mars spacecraft are about to get some of the closest views yet of an interstellar object that's currently passing through our Solar System.
Comet 3I/ATLAS was discovered on 1 July 2025, and has since been observed and tracked by some of our most powerful telescopes, both on Earth and in space.
The comet is passing through our Solar System, having arrived here from elsewhere in the Galaxy, and is one of only three such bodies ever discovered.
3I/ATLAS about to disappear behind the Sun from our perspective on Earth, and won't be visible again until early December 2025, when it emerges into our sky again.
Frustratingly, this period marks the point at which it will be most active.
So how can we continue to observe this interstellar object?
Humanity has a trick up its sleeve, in the form of the spacecraft we've sent to other planets across the Solar System.
3I/ATLAS from Mars
Between 1 and 7 October, the European Space Agency's Mars orbiters – Mars Express and ExoMars Trace Gas Orbiter – are scheduled to observe comet 3I/ATLAS as it passes close to the planet.
ESA says the closest distance between the spacecraft and the comet will be 30 million km (18.6 million miles), which will occur on 3 October 2025.
Mars Express and ExoMars Trace Gas Orbiter are well-established missions, having been exploring Mars since 2003 and 2016, respectively.
There hasn't been enough time to build and launch a dedicated mission to visit and explore 3I/ATLAS, so these orbiters will be carrying out observations of the comet from their unique vantage point at the Red Planet.
ESA’s Mars Express and ExoMars Trace Gas Orbiter (TGO) will observe the comet with several instruments around its closest approach to Mars on 3 October 2025.
On that date, 3I/ATLAS will be around 30 million km from Mars.
These missions are well equipped to carry out some of the vital science that astronomers want to achieve before 3I/ATLAS exits our Solar System.
Mars Express will use its High Resolution Stereo Camera (HRSC), while and ExoMars TGO will use its Colour and Stereo Surface Imaging System (CaSSIS).
Both cameras were designed to photograph the Red Planet, but for a brief moment they'll be pointed at 3I/ATLAS.
ESA says they'll be able to measure the spectrum of light from the comet using Mars Express’s OMEGA and SPICAM spectrometers and TGO’s NOMAD spectrometer.
This could give scientists vital information about the activity occurring at the comet's surface as it approaches the Sun.
It could even reveal more about what 3I/ATLAS is made of.
What images will we get?
So are we about to get more spectacular images of 3I/ATLAS, like those captured by the Hubble Space Telescope, for example?
Unfortunately not, according to ESA.
The cameras on these spacecraft were designed to photograph the surface of Mars from Mars orbit, and won't be able to pick out much detail on such a relatively small comet 30 million km away.
But the cameras may be able to capture images of its long tail and also gather data that scientists can use to find out more about what 3I/ATLAS is made of.
NASA has also said that its Perseverance and Curiosity Mars rovers will observe 3I/ATLAS at the beginning of October, and that its Mars Reconnaissance Orbiter will attempt to view the comet.
However, no details have yet been given by NASA as to exactly what its spacecraft will be looking for, or what sort of scientific data they might be able to gather.
Once 3I/ATLAS passes Mars, there will be further opportunities to acquire images and data.
Following the Mars fleet's views of 3I/ATLAS, ESA says in November 2025, it will then be the turn of the Juice mission to catch a glimpse of the comet.
Juice (Jupiter Icy Moons Explorer) is on its way to Jupiter, where it will explore the planet's largest icy moons to search for signs of habitability, but will be in a good position to take a look at the comet.
What will Juice see when it turns its cameras to 3I/ATLAS? Time will tell.
