On 2 October 2025, MRO turned away from Mars to image 3I/ATLAS, only the third interstellar object ever observed passing through our solar system!

In this 3.2 second exposure, HiRISE successfully detected 3I/ATLAS at a scale of 30 km/pixel and a spacecraft distance of roughly 30 million kilometers (19 million miles). However, MRO is not well-suited to exposures of this length. The nucleus, estimated from Hubble Space Telescope images to be at most a few kilometers across, cannot be resolved in our HiRISE image. Additionally, due to spacecraft jitter during the observation period, 3I/ATLAS is smeared by several pixels. Refinement of the data continues, but we can clearly see the coma. In fact, the full coma spans our entire HiRISE image, but only the brightest inner region is detected given the exposure time used. (See an annotated version here).

Throughout October, 3I/ATLAS was too close to the Sun in Earth’s sky to be visible from most telescopes, giving MRO a unique view of the coma. While the comet will pass no closer than 270 million kilometers from Earth, it came within 30 million kilometers of Mars.

ALL IMAGE PRODUCTS
ESP_089922_9080
ESP_089922_9081 (Our cutout is derived from this product)
ESP_089923_9080
ESP_089923_9081

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NASA/JPL-Caltech/University of Arizona
#Mars #science #NASA