Interpretation of the band in the new image of 3i / Atlas of the Perseverance Rover camera | By Avi Loeb | October 2025
On October 4, 2025, at the average local solar time of 21:33:39 on Mars, the good navigation camera (Navcam) on Mars Perseverance Rover took an image (published online by NASA here and here) of the interstellar object 3i / Atlas in the Martian sky. At that time, 3i / Atlas was a distance of around 38 million kilometers from March.
The image shows an elongated strip which is about 4 times longer than wide. This band has raised questions about social media as to whether 3i / Atlas is a large cylindrical object. I was asked for my opinion on this confusing image of the representative Anna Paulina Luna and I therefore immediately developed the following figures.
The Navcam on the Rover of Perseverance has a sensitivity to visible light with an angular resolution of 0.33 milli-raadian (or in an equivalent manner 68 seconds of arcs) by Pixel, as detailed here. This results in a space scale of around 12,500 kilometers at the distance of 3i / Atlas of Mars when the image was taken. This scale defines the width of the elongated band in the 3i / Atlas Navcam image. Thus, the projected length of the band is around 50,000 kilometers.
The upper limit on the diameter of 3i / Atlas was derived by the Spatial Spherex observatory (reported here) at 46 kilometers for an albedo of 4%. The Navcam band is a thousand times longer than this upper limit and must therefore be an artifact of a long time of integration since the source moves through the Martian sky. If 3i / Atlas was a cylinder up to 50,000 kilometers, he would then have occupied an angular size of 23 seconds of arc in the image of the Hubble space telescope taken on July 21, 2025, when 3i / Atlas was 3 times the separation of the Sun-Sun from the Hubble camera. Instead, 3i / Atlas seems smaller by at least an order of magnitude in the real Hubble image (available here and here). This suggests that the lengthening of the band has been generated by the integration time used to make the Navcam composite image, during which 3i / Atlas moved to the Martian sky.
Mars orbit the sun at a speed of 24 kilometers per second. 3i / Atlas moves on a retrograde orbit in the direction opposed to Mars at a speed of approximately 67 kilometers per second compared to the sun. The speed of 3i / Atlas compared to Mars results in a length of the path of approximately 50,000 kilometers for an integration time of 10 minutes.
In conclusion, the Navcam image band must have resulted from the stack of hundreds of Navcam images over a total interval of approximately 10 minutes. 3i / Atlas would have looked like a circular place for an individual snapshot, which has a maximum exposure time of 3.28 seconds for Navcam. In a single frame, the 3i / Atlas movement on the Martian sky would have coated its image of only 300 kilometers, or only about 3% of the much larger maculinage of 12,500 kilometers associated with the limited angcam limited resolution. The stack of hundreds of images improved the apparent brightness of 3i / Atlas in the final image.
A way of thinking of the band is like a sequence of maculé clichés, like a pod of green beans. 3i / Atlas shared the experience of a movie star with many March 7 orbiters cameras and a rover on the ground taking snapshots while it crossed the Martian sky.
The highest image was taken by the Hrise camera aboard the Mars recognition orbiter. Hrise has an angular resolution which resulted in 30 kilometers per pixel on October 3, 2025. The brightest pixel in the Hrise image will provide the best constraint to date on the 3i / Atlas area. We all hope that the Hrise team will publish their images as soon as possible.
About the author
AVI counts is the project manager Galileo, founding director of the Harvard University-Black Hole Initiative, director of the Institute for Theory and Computation of the Harvard-Smithsonian Center for Astrophysics, and the former president of the Department of Astronomy of Harvard University (2011-2020). He is a former member of the Council of the Chairman of Councilors on Sciences and Technology and former Chairman of the Board of Directors of Physics and Astronomy of National Academies. He is the successful author of “Alien: The first sign of intelligent life beyond the earth“And co-author of the manual”Life in the cosmos“, Both published in 2021. The pocket edition of his new book, entitled”Interstellar“Was published in August 2024.
