NASA on 2 October 2025 released a set of new observations that represent the closest imaging of interstellar comet 3I/ATLAS so far, with the Mars Reconnaissance Orbiter (MRO) capturing the object from about 30 million kilometers (19 million miles). The comet was first detected by the ATLAS survey on 1 July 2025 and reached perihelion on 29 October 2025 while Earth was on the far side of the Sun. Multiple NASA-supported assets — from Mars orbiters and a Mars rover to solar observatories and asteroid-bound spacecraft — collected complementary views across optical and ultraviolet wavelengths. Those coordinated observations, now public, set the stage for further study as 3I/ATLAS makes its closest approach to Earth on 19 December 2025.
Key Takeaways
- Discovery: 3I/ATLAS was identified by the ATLAS survey telescope on 1 July 2025, flagged as an object with an interstellar trajectory.
- Closest Mars imaging: MRO imaged the comet on 2 October 2025 from ~30 million km (19 million mi), the tightest direct remote sensing to date.
- Perihelion timing: The comet passed its closest point to the Sun on 29 October 2025, when Earth-based viewing was geometrically unfavorable.
- Multi-wavelength coverage: MAVEN observed ultraviolet hydrogen signatures on 28 September 2025, while MRO provided optical imaging and Perseverance observed from the Martian surface.
- Solar and outer-orbit assets: PUNCH, STEREO, SOHO, and the asteroid-mission spacecraft LUCY and Psyche also recorded sightings from their solar-orbit vantage points.
- Image quality: Most images are low-resolution or slightly fuzzy but nonetheless valuable for compositional and dynamical analysis.
- Public sighting: An astrophotographer in New Mexico captured a notable image on 16 November 2025 showing a green coma and pronounced tails consistent with cometary activity.
Background
Interstellar visitors are rare and scientifically prized because they carry material formed around other stars. Two earlier examples — 1I/‘Oumuamua in 2017 and 2I/Borisov in 2019 — each taught astronomers different lessons about non-native small bodies. 3I/ATLAS joins this short list and is unusual in its observable activity and orbital path, prompting a rapid global observing campaign after its 1 July 2025 discovery.
Cometary activity typically peaks near perihelion, as ices sublimate and create a coma and tails. For 3I/ATLAS, perihelion on 29 October 2025 occurred while Earth lay on the opposite side of the Sun, complicating Earth-based observations. Fortunately, a fleet of spacecraft distributed through the inner Solar System and at different solar longitudes enabled an alternative observing geometry that partially compensated for that disadvantage.
Main Event
NASA announced the release of a suite of images and supporting data gathered by missions that diverted observing time to track 3I/ATLAS as it transited the inner Solar System. The most proximate views came from Mars: MRO acquired optical images on 2 October 2025 from roughly 30 million kilometers (19 million miles), offering the highest-resolution remote snapshots to date.
MAVEN observed the comet in ultraviolet on 28 September 2025, isolating hydrogen emissions that help quantify volatile release and the structure of the coma and tail. Perseverance monitored the sky from Jezero Crater, providing a ground-based Martian perspective. NASA’s solar-focused observatories — PUNCH, STEREO, and the joint NASA–ESA SOHO mission — recorded the passage from their solar-orbit vantage points, while asteroid missions LUCY and Psyche noted detections en route through the asteroid belt.
Agency scientists stressed that the photos tend to be fuzzy compared with typical close-up mission imagery, yet every frame and spectrum carries measurable signals. As NASA planetary scientist Tom Statler explained at the briefing, the geometry worked against Earth during perihelion, but Mars and several other assets were fortunately positioned to observe the comet at critical times.
NASA officials also addressed public speculation: the observing teams and available spectra show comet-like activity and composition rather than engineered structure. An astrophotographer’s image from New Mexico taken on 16 November 2025 further supported a natural cometary appearance, showing a greenish coma and extended tails consistent with gas and dust emissions.
Analysis & Implications
These multi-platform observations will let researchers cross-check measurements of gas and dust production rates, estimate volatile inventory, and refine models of how an interstellar object reacts to solar heating. Ultraviolet hydrogen detections from MAVEN are particularly useful for assessing water and related volatiles, because hydrogen in the coma often traces water photodissociation.
Mars-based vantage points reduce some geometric ambiguities present in Earth-only datasets; combining Martian and solar-orbit observations improves trajectory refinement and allows triangulation of coma structure. That in turn helps constrain nucleus size estimates and non-gravitational accelerations that may result from outgassing.
On a larger scale, data from 3I/ATLAS will inform population-level questions about material transport between stellar systems: how common volatile-rich interstellar bodies are, and whether they resemble Solar System comets or represent a distinct class. Upcoming Earth-based observing opportunities around the 19 December 2025 closest approach will be key for higher-resolution spectroscopy and long-term photometric monitoring.
Comparison & Data
| Date | Observer / Platform | Distance / Note | Wavelength / Purpose |
|---|---|---|---|
| 1 July 2025 | ATLAS (survey telescope) | Discovery | Optical / detection |
| 28 Sep 2025 | MAVEN (Mars orbiter) | — | Ultraviolet / hydrogen in coma |
| 2 Oct 2025 | MRO (Mars orbiter) | ~30 million km (19 million mi) | Optical / closest remote imaging |
| 16 Nov 2025 | Astrophotographer (New Mexico) | Ground-based | Optical / visible coma & tails |
| 29 Oct 2025 | — | Perihelion (opposite Earth) | — |
| 19 Dec 2025 | Earth-based telescopes | Closest approach to Earth | Optical & spectroscopic opportunities |
The table summarizes primary observing milestones and the roles different platforms played. While the MRO and MAVEN observations give direct in-situ-like perspectives from Mars orbit, solar observatories and asteroid-mission spacecraft supplied complementary views that help fill temporal and geometric gaps in the dataset.
Reactions & Quotes
NASA officials framed the observations as an opportunistic scientific success enabled by a distributed fleet of spacecraft. Below are representative remarks and their context.
“Comet 3I/ATLAS reached perihelion when Earth was on the wrong side for convenient observation, but Mars was favorably placed, so our Mars assets were able to observe the comet.”
Tom Statler, NASA planetary scientist
Statler’s comment highlighted why Mars orbiters produced the highest-resolution remote images and how mission geometry determined which platforms could contribute.
“The comet was right inside the orbit of Mars, and that positioned our missions well to collect critical data.”
Nikki Fox, NASA Science Mission Directorate associate administrator
Fox emphasized the serendipity of platform placement and the resulting scientific payoff.
“This object is a comet. It looks and behaves like a comet and all evidence points to it being a comet. But this one came from outside the Solar System, which makes it fascinating, exciting, and scientifically very important.”
Amit Kshatriya, NASA associate administrator
Kshatriya addressed public speculation directly, noting that current datasets support a natural, cometary origin rather than artificial explanations.
Unconfirmed
- The precise nucleus size and bulk density of 3I/ATLAS remain uncertain pending higher-resolution imaging or indirect size constraints.
- No perihelion images have been released that show the comet at its absolute peak activity; available datasets are pre- and post-perihelion snapshots.
- Any social-media claims that the object is artificial or non-cometary lack supporting evidence and remain unsubstantiated.
Bottom Line
Coordinated observations from Mars orbit, the Martian surface, solar observatories, and distant asteroid missions have given astronomers the best remote look yet at an interstellar comet. Although many images are modest in resolution, the combined optical and ultraviolet datasets are scientifically rich and will enable improved estimates of volatile content, outgassing behavior, and dynamical response to solar heating.
As 3I/ATLAS approaches its closest point to Earth on 19 December 2025, ground-based telescopes and spectrographs will have a renewed opportunity to capture higher-signal measurements. Those follow-up observations, combined with the Mars- and space-based archive, should clarify outstanding questions about composition and help place 3I/ATLAS in the broader context of interstellar small bodies.