Interstellar comet 3I/ATLAS made its closest pass to Mars on Oct. 3, and Red Planet spacecraft were ready for it.
The NASA-funded ATLAS survey telescope in Chile first observed the comet on July 1, marking the third ever interstellar object to be tracked through our solar system after 1I/`Oumuamua and 2I/Borisov.
As it approaches the Sun, comet 3I/Atlas is no longer visible to Earth’s ground-based telescopes, leaving it up to spacecraft to keep eyes on this interstellar wanderer.
Two European Space Agency (ESA) orbiters, the ExoMars Trace Gas Orbiter and Mars Express used cameras to watch for the comet passing about 18.5 million miles (30 million km) away.
According to the ESA, mission scientists weren’t sure how well these images would turn out with a dim target so far away. Normally, these instruments are used to image objects more than 1,000 miles below. The Color and Stereo Surface Imaging System (CaSSIS) on ExoMars wasn’t designed for this kind of imaging.
The GIF below from ExoMars shows the plan paid off, as the comet can be seen moving across the center of the image.
ExoMars TGO images comet 3I/ATLAS taken in October 2025.
(ESA / FOX Weather)
“This was a very challenging observation for the instrument. The comet is around 10,000 to 100,000 times fainter than our usual target,” Nick Thomas, CaSSIS principal investigator said.
ESA said so far, the comet has yet to appear in any Mars Express images because images were taken with half-second exposures, meaning a lot more data to look through. The ExoMars spacecraft took images at five-second exposure times.
Still, ESA scientists will continue to look through the data from both Mars spacecraft for the faint comet zooming closer to the Sun.
Comet 3I/Atlas is expected to make its closest approach to the Sun on Oct. 30, reaching about 130 million miles (210 million km) from our star.
ESA said its Jupiter Icy Moons Explorer (Juice) will next observe the comet on Nov. 2 and Nov. 25. However, it won’t be as close to the spacecraft as the Mars flyby, and ESA won’t receive this data until early next year.
NASA’s Juno spacecraft would be another mission that could look for the comet. However, it’s unclear if the spacecraft is still operational. The Juno mission was extended through Sept. 30, and with the ongoing U.S. government shutdown, NASA is not providing updates on the mission.
New image of the comet 3I/ATLAS from the Hubble Telescope
(NASA)
NASA previously released observations of the comet by space telescopes, Hubble and James Webb, as well as the SPHEREx mission. The space agency said it planned to observe comet 3I/Atlas with its Mars spacecraft and its rovers on the Red Planet, as well as five additional ongoing deep space missions.
NASA’s Mars missions are continuing to operate during the shutdown as planned, but the agency won’t be updating its website or social media platforms during the government’s hiatus.
