Interstellar comet 3I/ATLAS is currently making its way through our Solar System, offering an incredible opportunity to observe an ancient relic from deep space.
The problem is, however, that 3I/ATLAS is soon set to disappear from view, as its trajectory takes it around the opposite side of the Sun, from Earth's perspective.
It then won't be visible from Earth-based telescopes until early December 2025, meaning we won't be able to see it from Earth when it's at its most active.
So how can astronomers and space scientists hope to learn more about 3I/ATLAS when it's not visible?
We can't launch a new, dedicated spacecraft to observe 3I/ATLAS in time.
But astronomers say there are other existing spacecraft at Mars, Jupiter and even the Sun itself, which could catch a glimpse of this interstellar visitor at a key stage in its journey.
A relic from the cosmic noon
One particular study into 3I/ATLAS examines the existing spacecraft dotted around the Solar System that might be able to take advantage of their vantage points and learn more about 3I/ATLAS.
The study, led by Thomas Marshall Eubanks, highlights an interesting reason why scientists are keen to learn so much about the comet.
The science team behind the paper say 3I/ATLAS is likely to be a remnant of our Milky Way galaxy's 'cosmic noon', having originated from the galaxy's 'thick disk'.
This means it could be a remnant from a key period in the Milky Way's history, around 9–13 billion years ago, when a period of intense star formation occurred.
"If confirmed, 3I will provide a means to explore the stellar and planetesimal formation process, and its astrobiological implications, in an early period of galactic history," the paper says.
However, 3I/ATLAS will reach its closest point to the Sun and become more active – and more unpredictable – when it's on the other side of the Sun from Earth.
Further analysis of 3I/ATLAS is clearly required, and that's where other spacecraft may be deployed to help.
Mars missions
The study authors point to two Mars spacecraft that will be able to observe 3I/ATLAS in the ultraviolet spectrum.
Namely the Emirates Mars Ultraviolet Spectrometer (EMUS) on the Hope spacecraft and
the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft.
Indeed, we already know that MAVEN is capable of capturing an image of a comet from Mars.
MAVEN photographed hydrogen gas surrounding comet C/2013 A1 Siding Spring on 17 October 2014, two days before the comet's closest approach to Mars. You can see this image above.
However, at the time the image was captured, C/2013 A1 was 8.5 million km (5.3 million miles) away.
During 3I/ATLAS's close approach to Mars, it will be much further, at 28 million km (18 million miles) from the Red Planet.
The European Space Agency says its Mars Express and ExoMars Trace Gas Orbiter (TGO) spacecraft will observe 3I/ATLAS on 3 October 2025, around the time of the comet's closest approach to Mars
Instruments on these spacecraft include Mars Express’s High Resolution Stereo Camera (HRSC) and ExoMars TGO’s Colour and Stereo Surface Imaging System (CaSSIS).
These cameras are used primarily to photograph the surface of Red Planet, but may be turned towards 3I/ATLAS to capture views of the comet from another world.
And ESA says they'll attempt to measure the spectrum of light from the comet using Mars Express’s OMEGA and SPICAM spectrometers and TGO’s NOMAD spectrometer.
That means these instruments will be able to study light from the comet and thereby reveal more about the comet's composition and chemical makeup.
"The observations may give us hints about the volatile activity and composition of 3I/ATLAS," ESA says.
However, ESA says comet 3I/ATLAS would only take up less than a pixel in images captured by Mars Express and the ExoMars Trace Gas Orbiter.
"We expect better images of the halo of gas around the comet and the tail that streams behind it," ESA says.
So perhaps we shouldn't expect anything spectacular, image-wise, from these missions, but instead, interesting science that astronomers can delve into.
Also, the paper says the Emirates Mars Mission may be able to gather data on 3I/ATLAS using its Infrared Spectrometer instrument.
And the study authors note that the NASA Curiosity and Perseverance Mars rovers "could both observe 3I at night from the surface of Mars during the period when it was closest to the planet."
They may be able to detect changes in the comet's brightness and the size of its 'coma', the fuzzy bulb of gas surrounding its nucleus, which should get bigger and become more active as 3I/ATLAS gets closer to the Sun.
Jupiter missions
There are three spacecraft intended for observations at the Jupiter system that could be used to get a new view of 3I/ATLAS, and those are NASA's Juno spacecraft and Europa Clipper, and the European Space Agency's Jupiter Icy Moons Explorer (Juice).
Juno is currently conducting polar orbits of Jupiter, while the Europa Clipper and Juice missions are primarily focussed on exploring Jupiter's largest moons for signs of potential habitability.
The European Space Agency says Juice is the spacecraft in its fleet likely to have the best view of 3I/ATLAS in its active state.
"Juice will attempt observations in November 2025 using several instruments, including cameras, spectrometers and a particle sensor," ESA says.
"Coordination with NASA’s Europa Clipper mission is being considered, in particular to observe using the twin ultraviolet spectrographs (one on each spacecraft)."
There has also been talk among scientists of using the Juno spacecraft to get a closer look at 3I/ATLAS in March 2026, but as such there are no definitive plans – that we could see – to do so.
Solar missions
Since comet 3I/ATLAS is going to get close to the Sun, wouldn't it make sense to point some of our Sun-studying spacecraft at it?
Spacecraft that could do so include the NASA/ESA SOHO spacecraft, NASA's STEREO-A and its PUNCH satellites, NASA's Parker Solar Probe and the European Space Agency's Solar Orbiter.
These spacecraft image the Sun and the regions close to it, so they may be able to capture images of 3I/ATLAS within their field of view.
SOHO, for example, captured an amazing image of comet C/2023 A3 Tsuchinshan-ATLAS back in October 2024.
However, ESA says "3I/ATLAS will pass through the field of view of the Solar and Heliospheric Observatory (SOHO), but we expect it to be much too faint to be visible."
The Parker Solar Probe has also photographed a comet before.
It imaged comet NEOWISE back in July 2020, shortly after that comet's close approach to the Sun, using its WISPR instrument (Wide-Field Imager for Solar PRobe).
The study authors say that Parker should be able to observe comet 3I/ATLAS with WISPR from late September to early November 2025, a time period that covers the comet's close approach to the Sun.
Other missions
The other potential existing missions that may be able to capture a glimpse of comet 3I/ATLAS include the Psyche mission, which is on its way to study asteroid 16 Psyche in 2029.
Psyche passed close by 3I/ATLAS on 4 September 2025, but as yet no images or science results have been publicly released showing that the mission did observe or image the comet.
Another spacecraft that could get a view of 3I/ATLAS is ESA's Hera mission, which is due to study the results of NASA's DART mission.
The DART spacecraft purposefully impacted into Didymos, a moonlet orbiting the asteroid Dimorphus, in September 2022 as part of a planetary defence test.
Hera is on its way to study the aftermath of this collision, to learn more about whether we would be able to successfully deflect a dangerous asteroid heading towards Earth.
And, potentially, the Lucy mission may get a glimpse of 3I/ATLAS, too.
Lucy is currently investigating Jupiter's mysterious Trojan asteroids, which share the gas giant planet's orbit around the Sun.
The study authors even suggest that Hera and Lucy may be able to sample the interstellar comet's tail.
Indeed, it's interesting to note just how big our fleet of spacecraft and rovers spread across the Solar System really is.
And how, as well as offering us detailed glimpses of other bodies like Mars, Jupiter, our Sun and distant asteroids, humanity has effectively given itself numerous eyes across the Solar System.
That means that, in the case of a chance visit from a distant object like 3I/ATLAS, which is merely passing through our Solar System, we've given ourselves every opportunity of learning as much as we can, while we can.
