# 3I/ATLAS

> 3I/ATLAS is the third object known to have entered the Solar System from interstellar space, found by the ATLAS survey in Chile on 1 July 2025 on an…

Source: https://mysteriesdept.com/mysteries/3i-atlas  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  
Updated: 2026-11-02T16:03:55+00:00  

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**MYS** 0DFPTE25MVWR·Mystery · object

# 3I/ATLAS

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3I/ATLAS

![Hubble image of 3I/ATLAS: a bright blue core in a teardrop-shaped haze, with background stars drawn out into short streaks](https://mysteriesdept.com/media/folio/3i-atlas-lead)

Hubble, 21 July 2025 · NASA, ESA, D. Jewitt (UCLA); J. DePasquale (STScI) · CC BY 4.0

Designation

3I/ATLAS = C/2025 N1 (ATLAS); first posted as candidate A11pl3Z⁠[[1]]

Discovered

1 July 2025, ATLAS 0.5-m telescope, Río Hurtado, Chile⁠[[1]]

Earliest images

TESS, from 7 May 2025, found afterwards⁠[[13]]

Orbit

Hyperbolic, eccentricity 6.12; inclination 175 degrees (retrograde)⁠[[26]]

Incoming speed

58.0 km/s relative to the Sun⁠[[63]]

Perihelion

1.36 au on 29 October 2025⁠[[8]]

Close approaches

Mars 0.19 au (3 October 2025); Earth 1.80 au (19 December 2025); Jupiter 0.36 au (16 March 2026)⁠[[8]]

Nucleus

Radius 1.3 ± 0.2 km for an albedo of 0.04⁠[[41]]

Inbound coma

Carbon dioxide 7.6 times water at 3.3 au⁠[[3]]

Water D/H

0.95 ± 0.06 per cent, about 30 times typical comets⁠[[6]]

Extra acceleration

4.6 × 10^-8 au per day squared at 1 au, peaking about 28 days after perihelion⁠[[26]]

Now

12.9 au from the Sun on 2 November 2026, magnitude about 25.6⁠[[8]]

Status

Unexplained

Questions

0 of 10 answered

People [**Adam Hibberd** Co-author of the paper raising the possibility that 3I is technology, and of the Juno intercept proposal](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARYQTS/adam-hibberd)[**Cyrielle Opitom** University of Edinburgh; first VLT spectrum and the CN isotope ratios](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARXJ47/cyrielle-opitom)[**Damien Hutsemékers** University of Liège; the nickel and iron measurements and the carbonyl explanation](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARW86Z/damien-hutsemekers)[**David Jewitt** UCLA astronomer; led the first Hubble observations, which limited the nucleus radius to below 2.8 km](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARZX30/david-jewitt)[**Davide Farnocchia** JPL; produced orbit solution 55 with its non-gravitational terms](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARTC6Z/davide-farnocchia)

All 10 people ›

[**John Tonry** ATLAS principal investigator; credited on the discovery circular and led the ATLAS photometry paper](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARRGWN/john-tonry)[**Larry Denneau** ATLAS team member credited with the discovery observations at ATLAS Chile](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARR0WH/larry-denneau)[**Man-To Hui** Led Hubble program 18152, which first separated the nucleus: radius 1.3 km](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARRPEE/man-to-hui)[**Martin A. Cordiner** NASA Goddard astrochemist; led JWST program 5094 and the CO2 and isotope results](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARS7G7/martin-a-cordiner)[**Nathan X. Roth** NASA Goddard; led the methane D/H, coma mapping and ALMA methanol papers](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARW3QY/nathan-x-roth)

Places [All 11](https://mysteriesdept.com/places?mystery=3i-atlas) [**ALMA, Chajnantor plateau, Chile** radio observatory](https://mysteriesdept.com/mysteries/3i-atlas/places/PLC0DFQ70ART6XY/alma-chajnantor-plateau-chile)[**ATLAS Chile, El Sauce Observatory, Río Hurtado** telescope site](https://mysteriesdept.com/mysteries/3i-atlas/places/PLC0DFQ70ARVTK1/atlas-chile-el-sauce-observatory-rio-hurtado)[**Palomar Observatory, California** observatory](https://mysteriesdept.com/mysteries/3i-atlas/places/PLC0DFQ70ARRJTK/palomar-observatory-california)[**Paranal Observatory (VLT), Chile** observatory](https://mysteriesdept.com/mysteries/3i-atlas/places/PLC0DFQ70ARY4NJ/paranal-observatory-vlt-chile)

Organisations [All 6](https://mysteriesdept.com/organisations?mystery=3i-atlas) [**ATLAS** NASA-funded sky survey run by the University of Hawaii, with telescopes in Hawaii, Chile and South Africa](https://mysteriesdept.com/mysteries/3i-atlas/organisations/ORG0DFQ70ARRH0M/atlas-asteroid-terrestrial-impact-last-alert-system)[**European Southern Observatory** Intergovernmental observatory that runs the VLT at Paranal](https://mysteriesdept.com/mysteries/3i-atlas/organisations/ORG0DFQ70ART71S/european-southern-observatory)[**IAU Minor Planet Center** The clearing house for positions and designations of small bodies](https://mysteriesdept.com/mysteries/3i-atlas/organisations/ORG0DFQ70ARZ4FB/iau-minor-planet-center)[**NASA** United States space agency](https://mysteriesdept.com/mysteries/3i-atlas/organisations/ORG0DFQ70ARX22D/nasa)

Concepts [All](https://mysteriesdept.com/concepts)

[Outgassing](https://mysteriesdept.com/concepts/CPT0DECW037EHK5/outgassing)[Stratigraphy](https://mysteriesdept.com/concepts/CPT0DECW01M0SC0/stratigraphy)

Catalog key**MYS** 0DFPTE25MVWR

3I/[ATLAS](https://mysteriesdept.com/mysteries/3i-atlas/organisations/ORG0DFQ70ARRH0M/atlas-asteroid-terrestrial-impact-last-alert-system) is the third object known to have come into the Solar System from another star. The ATLAS survey's telescope at Río Hurtado in Chile recorded it on 1 July 2025, and within a day its orbit showed it could not be bound to the Sun: it arrived at 58 km/s on a path with an eccentricity above 6⁠[[1]]⁠[[2]]. Unlike 'Oumuamua, it had a coma from the first images. It was a comet.

For the next four months it was followed by most of the world's large telescopes and more than a dozen spacecraft, from Mars orbit to the Jupiter-bound Juice. What they found was a comet unlike ours: a coma made mostly of carbon dioxide, nickel vapour without iron, too little ammonia and carbon chains, dust that polarises light more strongly than any comet's, and water and methane richer in deuterium than any yet measured⁠[[3]]⁠[[4]]⁠[[5]]⁠[[6]]⁠[[7]]. The isotopes point to a very cold birthplace around a star poorer in heavy elements than the Sun, perhaps 10 to 12 billion years ago.

It is now on its way out, 12.9 au from the Sun and fainter than magnitude 25⁠[[8]]. A preprint in July 2025 asking whether it was alien technology drew most of the public attention⁠[[9]]; the measurements since describe a comet⁠[[10]]. What is still argued over is how big it is, which ice pushes it, how old it is, and why it changed so much after perihelion. Of the 10 questions on this site, 0 are answered.

### Key questionsset by the editors

[**How big is the nucleus of 3I/ATLAS?** ](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0JS9W15Y/how-big-is-the-nucleus-of-3i-atlas)No answer ahead yet

[**Is 3I/ATLAS a natural comet or a technological object?** ](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0N9WT65H/is-3i-atlas-a-natural-comet-or-a-technological-object)No answer ahead yet

[**What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?** ](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0HS0K7SD/what-is-3i-atlas-made-of-and-why-is-its-chemistry-so-unlike)No answer ahead yet

[**What pushes 3I/ATLAS off a purely gravitational path?** ](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0M0GNENV/what-pushes-3i-atlas-off-a-purely-gravitational-path)No answer ahead yet

[**Where in the Galaxy, and how long ago, did 3I/ATLAS form?** ](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form)No answer ahead yet

[**Why did 3I/ATLAS's activity and chemistry change so much across perihelion?** ](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0NWRSHDV/why-did-3i-atlass-activity-and-chemistry-change-so-much)No answer ahead yet

 [All 10 questions ](https://mysteriesdept.com/questions/key-questions?mystery=3i-atlas)

### Research sessions1 so far · last 2 Nov

`S-001`[3I/ATLAS opened: the literature to November 2026](https://mysteriesdept.com/mysteries/3i-atlas/sessions/SES0DFQC03S98K5/session-1-3i-atlas-opened-the-literature-to-november-2026)

2 Nov **39** evidence**10** questions raised**18** answers proposedNo question changed standing

 [All 1 sessions ](https://mysteriesdept.com/mysteries/3i-atlas/sessions)

## What happened

The ATLAS survey's 0.5-m telescope at Río Hurtado took four 30-second images of a faint moving object on 1 July 2025. Within a day the Minor Planet Center had named it 3I/ATLAS, and S. Deen, who measured the early images, reported that it looked fuzzy⁠[[1]]⁠[[11]]. Older images turned up quickly: ATLAS's own from Sutherland on 5 June, ZTF's from mid-June, the new Rubin Observatory's from 21 June, and TESS's from as early as 7 May, when it was beyond 6 au⁠[[12]]⁠[[13]]. It was already active there, and probably had been since about 9 au⁠[[14]].

Its path took it close to the plane of the planets and near Mars, Venus and Jupiter, but never closer to Earth than 1.8 au⁠[[8]]. From August the large telescopes and space observatories took spectra: JWST, SPHEREx, Hubble, Swift, the VLT, Keck, Gemini, ALMA and others⁠[[3]]⁠[[15]]⁠[[16]]. In early October it passed 29 million km from Mars, and the orbiters there imaged it; ESA used their positions to improve its orbit tenfold⁠[[17]]⁠[[18]]⁠[[19]]⁠[[20]].

Perihelion came on 29 October at 1.36 au, while it was on the far side of the Sun from Earth. Coronagraphs on STEREO-A, SOHO and GOES-19 and the PUNCH mission kept watch, and saw it brighten very steeply⁠[[21]]⁠[[22]]. ESA's Juice, the nearest spacecraft, measured its water in November⁠[[23]]. On 19 November [NASA](https://mysteriesdept.com/mysteries/3i-atlas/organisations/ORG0DFQ70ARX22D/nasa) released images from more than a dozen missions and called it a comet⁠[[10]]. Telescopes followed it out through the winter and spring of 2026; it passed Jupiter on 16 March, and no observation by Juno has been reported⁠[[8]]⁠[[24]]. The results kept arriving: the deuterium in its water in Nature in June 2026, the carbon and nitrogen isotopes in July, the methane deuterium at the end of October⁠[[6]]⁠[[25]]⁠[[7]]. JPL's latest orbit, of 21 October 2026, was made to support a new JWST programme⁠[[26]].

**Map of the world** [Open the full map](https://mysteriesdept.com/mysteries/3i-atlas/map)

[Chile][World]

[+][−]

1

**ATLAS Chile, El Sauce Observatory, Río Hurtado** Telescope site

Within 1 km

2

**ATLAS South Africa, Sutherland** Telescope site

Within 1 km

3

**Palomar Observatory, California** Observatory

Within 1 km

4

**Vera C. Rubin Observatory, Cerro Pachón** Observatory

Within 1 km

5

**Paranal Observatory (VLT), Chile** Observatory

Within 100 m

6

**Maunakea Observatories, Hawaii** Observatory

Within 1 km

7

**ALMA, Chajnantor plateau, Chile** Radio observatory

Within 1 km

8

**Roque de los Muchachos Observatory, La Palma** Observatory

Within 1 km

9

**Teide Observatory, Tenerife** Observatory

Within 1 km

10

**Hobby-Eberly Telescope, McDonald Observatory, Texas** Telescope

Within 100 m

MappedWithin 1 kmNatural Earth

### Timeline

**Timeline**

Squeezed where little happened. Each mark is a published claim, by how it stands:AcceptedMost likelyStill possibleDisputedRuled out

## What was measured

Composition. Inbound at 3.3 au JWST found carbon dioxide at 7.6 ± 0.3 times water, among the highest ratios seen in any comet⁠[[3]]; SPHEREx traced the CO2 coma out to at least 420,000 km⁠[[15]]. CN appeared near 3 au with carbon chains strongly depleted⁠[[27]]; ammonia's products, NH and NH2, were scarce⁠[[28]]; methanol was among the most abundant relative to HCN of any comet⁠[[29]]; and the ion tail was rich in nitrogen⁠[[30]]. Near perihelion the balance shifted: the coma became water-dominated, CO2 fell to about a tenth of water, and by late December CO was the most abundant gas⁠[[31]]⁠[[23]]⁠[[32]]. Methane was first detected in mid-December⁠[[33]].

Nickel and iron. From 3.1 au the VLT saw nickel atoms in the coma with no iron; iron appeared only inside 2.6 au, and the total metal output was at least ten times other comets'⁠[[34]]⁠[[4]].

Isotopes. Water's deuterium-to-hydrogen ratio is 0.95 ± 0.06 per cent by JWST and above 0.66 per cent by ALMA, some 30 times typical comets; carbon-13 is depleted in CO and CO2; methane's D/H is 3.3 per cent, 14 times comet 67P's; and the carbon and nitrogen ratios in CN are high⁠[[6]]⁠[[35]]⁠[[7]]⁠[[25]].

Dust. Its light shows a negative polarisation of -2.7 to -2.9 per cent at small phase angles, deeper than any asteroid or comet, unchanged across perihelion⁠[[5]]⁠[[36]]. Its silicates are amorphous, with no measurable crystals⁠[[37]]. Whether water ice was seen in the coma is disputed⁠[[38]]⁠[[39]]⁠[[40]].

Size and motion. Hubble first limited the nucleus to a radius below 2.8 km, then separated it from the coma: 1.3 ± 0.2 km for a comet-like albedo⁠[[16]]⁠[[41]]. Its orbit needs a small push beyond gravity, about 4.6 × 10^-8 au per day squared at 1 au, peaking a month after perihelion⁠[[26]]⁠[[42]]. Its rotation period was measured at about 16 hours before perihelion and about 7 hours after⁠[[43]]⁠[[44]]. Four radio searches found no transmitters⁠[[45]]⁠[[46]]⁠[[47]]⁠[[48]].

## The explanations

Most of the oddities have a natural reading. The isotopes, the scarce ammonia and the amorphous silicates fit a body that formed in a very cold disc around a metal-poor star⁠[[6]]⁠[[49]]⁠[[50]]. A second reading holds that cosmic rays reworked its outer 15 to 20 m over billions of years, so the CO2-rich gas seen inbound came from a crust rather than the original ice⁠[[51]]⁠[[52]]; the fall in CO2 after perihelion fits that, though it also fits ordinary heating of deeper, water-richer [layers](https://mysteriesdept.com/concepts/CPT0DECW01M0SC0/stratigraphy)⁠[[53]]. The nickel without iron is best explained by metal carbonyls, which sublimate far colder than metal-bearing dust⁠[[4]]⁠[[54]]. The polarisation is fitted by porous aggregates of tiny grains⁠[[36]]⁠[[55]].

The size was argued over from September 2025, when an analysis of early positions found no extra acceleration and inferred a nucleus above 5 km⁠[[56]]. The acceleration was detected once the arc reached perihelion, and the Hubble measurement put the radius near 1.3 km⁠[[42]]⁠[[41]]. Balancing the push against the gas lost gives a diameter of about a kilometre⁠[[57]]; the exact size depends on whether carbon dioxide or water carries the push, which the orbit alone cannot tell⁠[[58]]⁠[[59]]. Water rates from the same SOHO/SWAN data differ eightfold between two analyses⁠[[60]]⁠[[61]].

The age is in dispute too. Its speed places it among an old population above 7.6 billion years in one model⁠[[62]] and in the thick disc in another⁠[[63]]; a traceback through Gaia finds no home star and favours the thin disc⁠[[64]], and a kinematic age of 3 to 11 billion years leaves room for an object younger than the Sun⁠[[65]].

The technology reading began with a preprint by [Hibberd](https://mysteriesdept.com/mysteries/3i-atlas/people/FIG0DFQ70ARYQTS/adam-hibberd), Crowl and [Loeb](https://mysteriesdept.com/records/FIG0CSKBRJJ6DGG/abraham-avi-loeb), who described it as largely a pedagogical exercise and noted that a path this close to the planets' plane, passing near three of them, was improbable⁠[[9]]. Loeb placed it at level 4 of a ten-point scale and later listed 22 features he called anomalies⁠[[66]]⁠[[67]]. Each has been answered with comet physics: the sunward anti-tail by ice grains surviving longer on the sunward side, in a paper Loeb co-wrote, and the rest point by point by Jason Wright⁠[[68]]⁠[[69]]. No radio signal was found, and by December 2025 Loeb said the object was most likely natural⁠[[70]].

### Published claims

**Published claims and their status**

| Year | Who | Claimed | Status | Reason |
|---|---|---|---|---|
| 2025 | Darryl Z. Seligman and colleagues⁠[2] | 3I/ATLAS is an active comet on a hyperbolic orbit from interstellar space, the third such object found. | Accepted | Every later observation, from a dozen spacecraft and most large telescopes, shows a comet⁠[10]. |
| 2025 | Adam Hibberd, Adam Crowl and Abraham Loeb⁠[9] | 3I/ATLAS might be alien technology, possibly hostile; its path near three planets is improbable by chance. | Disputed | Four radio searches found nothing⁠[47], the push matches the gas lost⁠[57], and Loeb later called it most likely natural⁠[70]. |
| 2025 | Matthew J. Hopkins and colleagues⁠[62] | 3I's speed places it in an old population, more than 7.6 billion years old, with a high water fraction. | Still possible | A Gaia traceback favours the thin disc⁠[64], while the isotopes point to great age⁠[6]. |
| 2025 | Aster G. Taylor and Darryl Z. Seligman⁠[65] | 3I's kinematic age is about 3 to 11 billion years. | Still possible | Consistent with both the thick- and thin-disc readings⁠[62]⁠[64]. |
| 2025 | Martin A. Cordiner and colleagues⁠[3] | 3I's coma is dominated by carbon dioxide, at 7.6 times water. | Accepted | Confirmed by SPHEREx⁠[15]; the ratio fell sharply after perihelion⁠[53]. |
| 2025 | Damien Hutsemékers and colleagues⁠[4] | Nickel without iron far from the Sun comes from metal carbonyls. | Most likely | After perihelion the metals followed CO, as carbonyls would⁠[54], but an extra early heat source may be needed⁠[76]. |
| 2025 | Zuri Gray and colleagues⁠[5] | 3I's dust has a deeper negative polarisation than any asteroid or comet. | Accepted | Confirmed after perihelion in optical and near-infrared polarimetry⁠[36]⁠[55]. |
| 2025 | Richard Cloete, Abraham Loeb and Peter Vereš⁠[56] | With no acceleration in the early arc, the nucleus must be more than 5 km across. | Ruled out | The acceleration was found in the full arc⁠[42] and Hubble measured a radius of 1.3 km⁠[41]. |
| 2025 | Yiyang Guo and colleagues⁠[64] | No nearby star is a plausible home for 3I, and a thin-disc origin is strongly favoured. | Still possible | Other kinematic studies place it in the thick disc⁠[63]; Gaia's next release will test it. |
| 2025 | Romain Maggiolo and colleagues⁠[51] | Cosmic rays reworked 3I's outer 15 to 20 m, so its CO2-rich, red surface is a crust made in transit. | Still possible | The composition did change after perihelion⁠[53], but deeper heating explains that too⁠[31]. |
| 2025 | Eric Keto and Abraham Loeb⁠[68] | The sunward anti-tail is ice grains surviving longer on the sunward side, not something unexplained. | Accepted | Anti-tails from large grains are long known in comets⁠[69]. |
| 2025 | Michael R. Combi and colleagues⁠[60] | 3I released 3.2 × 10^29 water molecules a second on 6 November 2025. | Disputed | A 3D model of the same data and Juice's spectrometer give 4 to 8 × 10^28⁠[61]⁠[23]. |
| 2026 | Man-To Hui and colleagues⁠[41] | Hubble separates the nucleus from the coma: a radius of 1.3 ± 0.2 km. | Accepted | Consistent with the size the acceleration implies⁠[57]; it scales with the assumed albedo. |
| 2026 | Martin A. Cordiner and colleagues⁠[6] | 3I's water and carbon isotopes show it formed below about 30 K around a metal-poor star, 10 to 12 billion years ago. | Most likely | Backed by ALMA's water D/H and the methane D/H⁠[35]⁠[7]; a cosmic-ray crust could alter surface ratios⁠[51]. |
| 2026 | Valentin Thoss, Abraham Loeb and Andreas Burkert⁠[58] | If carbon dioxide drives the push, the nucleus is 0.42 km in radius. | Still possible | The orbit fits CO2, water and CO activity laws equally well⁠[59]. |
| 2026 | Cristina A. Thomas and colleagues⁠[37] | 3I's silicates are amorphous and pyroxene-rich, with no measurable crystals. | Accepted | Matches an earlier MIRI study⁠[77]; unlike Solar System comets. |
| 2026 | Małgorzata Królikowska, Federico Spada and Luke Dones⁠[59] | The non-gravitational acceleration is robust, but the orbit cannot tell which gas drives it. | Accepted | Agrees with the systematics study⁠[42] and JPL's fit⁠[26]. |

## What would settle it

3I is too faint now for most telescopes and cannot be reached by a spacecraft. What is left is the data already taken, and a few more observations by the largest instruments.

The size can be settled from the last Hubble visits of program 18152, beyond 5 au, when the coma was faintest⁠[[71]]. Which gas pushes it can be settled by refitting the full set of 8,000-odd positions with the acceleration tied to the measured CO2 and water production curves rather than to standard laws⁠[[72]]⁠[[73]]. JPL's orbit solution 55 was made to support JWST program 13145; positions far out on the outbound leg will show whether the push has stopped, as [outgassing](https://mysteriesdept.com/concepts/CPT0DECW037EHK5/outgassing) predicts⁠[[26]]. The eightfold disagreement over water needs both hydrogen-coma models run on the same SOHO/SWAN frames⁠[[60]]⁠[[61]]. The age will be tested again when Gaia's next data release allows a better traceback⁠[[64]].

The larger test is more objects like it. The Rubin Observatory, which found 3I in its own commissioning images, began its ten-year survey in 2026 and is expected to find more interstellar objects⁠[[12]]⁠[[74]]. ESA's Comet Interceptor, due to launch in late 2028 or early 2029, could fly past one if it is reachable⁠[[75]].

## Questions

0 of 10 questions are answered.

**Key questions** [All 10](https://mysteriesdept.com/questions/key-questions?mystery=3i-atlas)

 **0**

[How big is the nucleus of 3I/ATLAS?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0JS9W15Y/how-big-is-the-nucleus-of-3i-atlas)

0 of 0 sub-questions answered·0

Open: 2 answers, none ahead



 **0**

[Is 3I/ATLAS a natural comet or a technological object?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0N9WT65H/is-3i-atlas-a-natural-comet-or-a-technological-object)

0 of 0 sub-questions answered·0

Open: no answer ahead yet



 **0**

[What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0HS0K7SD/what-is-3i-atlas-made-of-and-why-is-its-chemistry-so-unlike)

0 of 2 sub-questions answered·0

Open: no answer ahead yet



 **0**

[What pushes 3I/ATLAS off a purely gravitational path?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0M0GNENV/what-pushes-3i-atlas-off-a-purely-gravitational-path)

0 of 1 sub-questions answered·0

Open: no answer ahead yet



 **0**

[Where in the Galaxy, and how long ago, did 3I/ATLAS form?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form)

0 of 0 sub-questions answered·0

Open: 2 answers, none ahead



 **0**

[Why did 3I/ATLAS's activity and chemistry change so much across perihelion?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0NWRSHDV/why-did-3i-atlass-activity-and-chemistry-change-so-much)

0 of 1 sub-questions answered·0

Open: no answer ahead yet



## Evidence 38 findings

[What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0HS0K7SD/what-is-3i-atlas-made-of-and-why-is-its-chemistry-so-unlike)8 findings

[An icy body from a cold, metal-poor disc around an old star](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ178MEYWB/an-icy-body-from-a-cold-metal-poor-disc-around-an-old-star)Still possible

+[JWST measured a water D/H ratio of 0.95 ± 0.06 per cent and 12C/13C of 141 to 191 in CO2 and 123 to 172 in CO, pointing to ices formed below about 30 K around a metal-poor star some 10 to 12 billion years ago.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3PX0VGG4/jwst-water-d-h-near-1-per-cent-and-high-carbon-13-ratios)Supported

+[ALMA found water D/H above 6.6 × 10^-3, at least 40 times Earth's oceans and 30 times typical comets, with a different instrument and method from JWST.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3Q9YB4XN/alma-confirms-deuterium-rich-water-independently)Supported

+[Methane in 3I has a D/H ratio of 3.33 ± 0.31 per cent, 14 ± 2 times that of comet 67P and the highest methane D/H measured anywhere.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3SR2JMMK/methane-d-h-the-highest-ever-measured)Supported

+[VLT spectra of CN give 12C/13C of 151 and 14N/15N of 363, both high for a comet, though the 3-sigma ranges are wide.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3T4VZPQZ/high-carbon-and-nitrogen-isotope-ratios-in-cn)Suggestive

+[Astrochemical models reproduce 3I's water D/H most readily at less than half the Sun's metallicity and densities near 10^4 per cubic centimetre, and a composition model places its host between [Fe/H] -0.8 and 0.0.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3TH6PKZY/models-reproduce-the-water-at-low-metallicity)Suggestive

+[JWST/MIRI found the dust's silicates amorphous and pyroxene-rich with no measurable crystalline fraction (below 5.3 per cent), unlike Solar System comets and closer to interstellar dust.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3TYE9F15/amorphous-silicates-closer-to-interstellar-dust)Suggestive

[A crust made by cosmic rays on the journey](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ17SXMJ3A/a-crust-made-by-cosmic-rays-on-the-journey)Still possible

+[Models of galactic cosmic-ray processing reproduce 3I's CO2 enrichment and red slope in the outer 15 to 20 m, and explain the late methane as layering made in transit with an exposure age of 0.9 to 3.1 billion years.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3VE858GD/cosmic-ray-processing-explains-the-co2-and-the-red-colour)Suggestive

+[The coma's CO2-to-water ratio fell from 7.6 ± 0.3 at 3.3 au inbound to about 0.1 near perihelion and stayed far below the inbound value at 2.9 au outbound.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3VTKN1HK/co2-to-water-ratio-fell-from-7-6-to-about-0-1)Supported

[How big is the nucleus of 3I/ATLAS?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0JS9W15Y/how-big-is-the-nucleus-of-3i-atlas)5 findings

[About a kilometre across, or a little more](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ1MV3GTQV/about-a-kilometre-across-or-a-little-more)Still possible

+[Hubble images from December 2025 to January 2026 separated the nucleus from the coma, giving a radius of 1.3 ± 0.2 km for an albedo of 0.04.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ47J4JQGK/hubble-detects-the-nucleus-radius-1-3-0-2-km)Supported

+[Balancing the measured mass loss against the non-gravitational acceleration gives a diameter of 0.82 to 1.05 km; Loeb's group gets a radius of 0.42 km if CO2 drives it and 0.74 to 1.15 km if water does.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ47T6M9BD/mass-loss-and-push-agree-on-a-kilometre-sized-body)Suggestive

[More than 5 km across](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ1P0P0QR0/more-than-5-km-across)Disputed

+[Fitting positions from 15 May to 23 September 2025, Cloete, Loeb and Vereš found no acceleration above about 3 × 10^-10 au per day squared, which with JWST's mass-loss rate implies a diameter above 5 km.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ48WD5C4Z/no-acceleration-in-the-early-arc)Speculative

−[The 5-km claim rested on finding no non-gravitational acceleration through September 2025; with the full arc, the acceleration is required by the data and JPL fits it at 4.6 × 10^-8 au per day squared at 1 au.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ485CADJ6/the-missing-acceleration-turned-up)Supported

−[Before perihelion Hubble limited the radius to below 2.8 km and SPHEREx to below 2.5 km, and after perihelion Hubble measured 1.3 ± 0.2 km.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ48E606F6/two-telescopes-put-the-radius-below-2-8-km)Supported

[What pushes 3I/ATLAS off a purely gravitational path?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0M0GNENV/what-pushes-3i-atlas-off-a-purely-gravitational-path)5 findings

[Gas escaping from the nucleus, as on any active comet](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ1PMTRVR2/gas-escaping-from-the-nucleus-as-on-any-active-comet)Still possible

+[JPL's orbit solution 55 fits a radial acceleration of (4.62 ± 0.48) × 10^-8 au per day squared at 1 au, with transverse and normal terms, peaking 28.5 ± 9.2 days after perihelion, when the comet was most active.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4K6NRKGN/the-push-peaks-a-month-after-perihelion-with-the-activity)Supported

+[The distant inbound arc fits gravity alone, while the full arc through perihelion requires a non-gravitational acceleration; its systematic uncertainties exceed the formal ones.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4KHHYF1R/gravity-alone-far-out-a-push-only-near-the-sun)Supported

+[Of three persistent jets seen after perihelion, one lay within half a degree of the projected transverse direction of the acceleration on 30 November 2025.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4KSH16TV/jets-line-up-with-the-acceleration)Suggestive

[A propulsion system on a technological object](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ1QPEV6YS/a-propulsion-system-on-a-technological-object)Still possible

+[Hibberd, Crowl and Loeb suggested a technological 3I might use perihelion for a "reverse Solar Oberth" manoeuvre, and Loeb later listed the acceleration among the object's anomalies.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4MBN43TN/a-manoeuvre-at-perihelion-was-proposed)Speculative

−[The size of the acceleration matches the measured mass loss of a body about a kilometre across, so no source beyond the escaping gas is needed.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4M1WENV2/the-push-matches-the-gas-lost)Supported

[Where in the Galaxy, and how long ago, did 3I/ATLAS form?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form)4 findings

[An old thick-disc body, older than the Sun](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ30WEZNY9/an-old-thick-disc-body-older-than-the-sun)Still possible

+[Placing 3I's 58 km/s speed and radiant in a model of the Galaxy's interstellar objects gives an age above 7.6 billion years (68 per cent range 7.6 to 14), and Eubanks and colleagues argue for a thick-disc origin 9 to 13 billion years ago.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ52C3MMCJ/population-model-older-than-7-6-billion-years)Suggestive

+[The JWST team reads the high carbon-13 ratios as material accreted 10 to 12 billion years ago, before the Galaxy's carbon-13 had built up, an age estimate independent of the orbit.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ52T02NDX/carbon-isotopes-date-the-ices-to-10-to-12-billion-years-ago)Suggestive

[A thin-disc body a few billion years old](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ335PRDVB/a-thin-disc-body-a-few-billion-years-old)Still possible

+[Tracing 3I back through Gaia DR3 finds 25 stellar encounters within 1 pc, none a plausible host, and strongly favours a thin-disc origin; a second study finds 93 nominal encounters within 2 pc over 10 million years.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ5327B9KS/gaia-traceback-favours-the-thin-disc-and-finds-no-home-star)Suggestive

+[Taylor and Seligman's kinematic age for 3I is about 3 to 11 billion years, with a 12 per cent chance its host had [Fe/H] at or below -0.4; a composition clock gives only a lower limit of 0.6 billion years.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ53AZ1YT9/kinematic-age-of-3-to-11-billion-years)Suggestive

[Is 3I/ATLAS a natural comet or a technological object?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0N9WT65H/is-3i-atlas-a-natural-comet-or-a-technological-object)5 findings

[A natural comet from another planetary system](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ33MX6KQN/a-natural-comet-from-another-planetary-system)Still possible

+[3I shows a dust coma, dust and ion tails, jets, and the gases of comets: CO2, water, CO, HCN, methanol, CN, methane, and N2+, CO+ and H2O+ ions, in unusual proportions.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ53J61SHT/its-gases-and-tails-are-a-comets)Established

+[At its 19 November 2025 briefing, with images from more than a dozen spacecraft, NASA said 3I "looks and behaves like a comet".](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ53VZEVM7/nasa-it-looks-and-behaves-like-a-comet)Supported

[A technological object](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ33XWJ6XP/a-technological-object)Still possible

+[Hibberd, Crowl and Loeb put the chance of an orbit this close to the ecliptic passing near Venus, Mars and Jupiter at below about 0.005 per cent, and Eldadi and colleagues rated 3I 4 on a 0-10 significance scale.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ54HVJ0KF/an-orbit-close-to-the-planets-plane-passing-near-three-of)Speculative

−[The Allen Telescope Array (1-9 GHz), Breakthrough Listen at Green Bank (1-12 GHz, down to 100 mW) and two FAST searches (narrowband to 2.9 mW, periodic to 0.15 W) found no artificial signal.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ542ADEGE/four-radio-searches-found-nothing)Supported

−[The sunward anti-tail is explained by ice grains surviving longer on the sunward side, in a paper Loeb co-wrote, and Jason Wright answered the other listed anomalies with known comet behaviour; by December 2025 Loeb said 3I was most likely natural.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ54ASXW5D/the-anti-tail-and-other-anomalies-have-comet-explanations)Supported

[Why did 3I/ATLAS's activity and chemistry change so much across perihelion?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0NWRSHDV/why-did-3i-atlass-activity-and-chemistry-change-so-much)2 findings

[Heat reached deeper, water-richer layers and icy grains](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ349ZM4Y8/heat-reached-deeper-water-richer-layers-and-icy-grains)Still possible

+[ESPRESSO spectra show the coma becoming water-dominated near perihelion, and SPHEREx in December 2025 found water emission forty times brighter and the water-ice absorption mostly gone.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ54QY5WR5/water-took-over-near-perihelion-the-ice-band-vanished)Supported

+[By 22-23 December 2025 CO was the most abundant gas, with water and CO2 each about 40 per cent of it, and methane was detected for the first time in an interstellar object only in mid-December.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ54XAFGSW/co-most-abundant-by-december-methane-appears-late)Supported

[Why did nickel vapour appear around 3I/ATLAS without iron, so far from the Sun?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0SJDC3TY/why-did-nickel-vapour-appear-around-3i-atlas-without-iron-so)3 findings

[Metal carbonyls sublimating from the nucleus](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ187PJFP2/metal-carbonyls-sublimating-from-the-nucleus)Still possible

+[From December 2025 to January 2026 the nickel and iron in 3I's coma followed the correlation between metals and CO seen in Solar System comets, and outbound the metals declined more slowly, as expected for carbonyls from centimetre depths.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ46MX9MYT/after-perihelion-the-metals-follow-co)Suggestive

+[VLT spectra show neutral nickel at every epoch from 3.14 au and iron only inside 2.64 au, with the nickel-to-iron ratio falling from extreme to normal and total metal output at least ten times other comets'; carbonyl release fits best.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4JNJ6RZ0/nickel-from-3-1-au-iron-only-inside-2-6-au)Supported

[A short-lived heat source released the early nickel](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ197S5Z8J/a-short-lived-heat-source-released-the-early-nickel)Still possible

+[Modelling the whole trajectory, Hutsemékers and colleagues find carbonyl sublimation does not reproduce the early nickel excess and invoke a transient heat source at 100 to 140 K, perhaps amorphous ice crystallising; JWST later saw possible crystalline ice at 5.7 au.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4K00TXQE/carbonyls-alone-miss-the-early-nickel-excess)Suggestive

[What kind of dust gives 3I/ATLAS its unusually deep negative polarisation?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0STJE1SH/what-kind-of-dust-gives-3i-atlas-its-unusually-deep-negative)1 finding

[Porous aggregates of tiny, weakly absorbing grains](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ19DTND2G/porous-aggregates-of-tiny-weakly-absorbing-grains)Still possible

+[The negative polarisation branch reached -2.7 per cent at 7 degrees before perihelion and -2.9 per cent at 5.5 degrees after it, essentially unchanged, and both optical and near-infrared polarimetry are fitted by porous aggregates of sub-micron monomers.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ475QVY2W/polarisation-unchanged-across-perihelion-fitted-by-porous)Supported

[Which gas carries the push: carbon dioxide, water or carbon monoxide?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0T1AWZRC/which-gas-carries-the-push-carbon-dioxide-water-or-carbon)2 findings

[Carbon dioxide carries the push](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ2GHJNKVY/carbon-dioxide-carries-the-push)Still possible

+[With CO2 as the driver, Thoss and colleagues find a 0.42-km radius and 1.6 × 10^11 kg mass; water-driven versions need an active area that conflicts with the observations, partly because much water sublimes in the coma.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4MJGW244/a-co2-driven-model-fits-water-models-strain-the-active-area)Suggestive

[Water carries the push](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ2MF9XR6J/water-carries-the-push)Still possible

−[Radio OH and SOHO/SWAN analyses find up to 80 per cent of the water came from an extended source of icy grains in the coma, which adds gas but no push to the nucleus.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ4MVJ784S/much-of-the-water-came-from-icy-grains-not-the-nucleus)Suggestive

[How much water did 3I/ATLAS release at its peak after perihelion?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0T8NXG7Q/how-much-water-did-3i-atlas-release-at-its-peak-after)3 findings

[Four to eight times 10^28 molecules a second](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ34QCZRCE/four-to-eight-times-10-28-molecules-a-second)Still possible

+[Juice's MAJIS spectrometer measured water production of 8 × 10^28 molecules a second on 2 November 2025, falling to 4 × 10^28 by 25 November, about 2,000 kg a second.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ554J37RY/juice-measured-8-falling-to-4-10-28-a-second)Supported

+[Re-analysing the SOHO/SWAN hydrogen coma with a three-dimensional Monte Carlo model gives a post-perihelion peak of about 4 × 10^28 molecules a second, with no outbursts and much of the water from icy grains.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ55AT4QTE/a-3d-model-of-the-swan-data-peaks-near-4-10-28)Supported

[About 3 × 10^29 molecules a second](https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ35CB0ADR/about-3-10-29-molecules-a-second)Still possible

+[Fitting the SOHO/SWAN hydrogen coma with their standard model, Combi and colleagues found 3.17 × 10^29 water molecules a second on 6 November 2025 at 1.40 au.](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ55HTM3KJ/swan-standard-model-3-17-10-29-on-6-november)Supported

## See also

 [

**1I/'Oumuamua** The first interstellar object seen in the Solar System, found in October 2017.

](https://mysteriesdept.com/mysteries/oumuamua) [

**Nebra Sky Disc** A bronze disc inlaid with gold sun, moon and stars, dug up by looters in 1999.

](https://mysteriesdept.com/mysteries/nebra-sky-disc) [

**Phosphine in the clouds of Venus** A 2020 report of phosphine gas in the clouds of Venus, not independently confirmed.

](https://mysteriesdept.com/mysteries/venus-phosphine) [

**Homo naledi and the Rising Star burial claims** Bones of a small-brained hominin found deep in South Africa's Rising Star cave.

](https://mysteriesdept.com/mysteries/homo-naledi-burials)

## References

1. 1.[IAU Minor Planet Center 2025. MPEC 2025-N12: 3I/ATLAS = C/2025 N1 (ATLAS).](https://mysteriesdept.com/sources/SRC0DFPZ6F4ASFC/mpec-2025-n12-3i-atlas-c-2025-n1-atlas)cited 6 times here**SRC** 0DFPZ6F4ASFC
1. 2.[Seligman, D., Micheli, M., Farnocchia, D. et al. 2025. Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS. The Astrophysical Journal Letters.](https://mysteriesdept.com/sources/SRC0CSKBD3C762B/discovery-and-preliminary-characterization-of-a-third)[doi](https://doi.org/10.3847/2041-8213/adf49a)cited 6 times here**SRC** 0CSKBD3C762B
1. 3.[Cordiner, M., Roth, N., Kelley, M. et al. 2025. JWST detection of a carbon dioxide dominated gas coma surrounding interstellar object 3I/ATLAS. arXiv.](https://mysteriesdept.com/sources/SRC0CSKBDB607EW/jwst-detection-of-a-carbon-dioxide-dominated-gas-coma)[doi](https://doi.org/10.3847/2041-8213/ae0647)cited 8 times here**SRC** 0CSKBDB607EW
1. 4.[Hutsemékers, D., Manfroid, J., Jehin, E. et al. 2025. Pre-perihelion evolution of the NiI/FeI abundance ratio in the coma of the interstellar comet 3I/ATLAS. From extreme to normal. A&A 706, A43.](https://mysteriesdept.com/sources/SRC0DFPWGSFD45Q/pre-perihelion-evolution-of-the-nii-fei-abundance-ratio-in)[doi](https://doi.org/10.1051/0004-6361/202557484)cited 4 times here**SRC** 0DFPWGSFD45Q
1. 5.[Gray, Z., Bagnulo, S., Borisov, G. et al. 2025. Extreme Negative Polarisation of New Interstellar Comet 3I/ATLAS. arXiv.](https://mysteriesdept.com/sources/SRC0DFPWGSF6D0A/extreme-negative-polarisation-of-new-interstellar-comet-3i)cited 2 times here**SRC** 0DFPWGSF6D0A
1. 6.[Cordiner, M., Roth, N., Micheli, M. et al. 2026. Isotopic Evidence for a Cold and Distant Origin of the Interstellar Object 3I/ATLAS. Nature 655, 870-874.](https://mysteriesdept.com/sources/SRC0DFPWGSFXVMV/isotopic-evidence-for-a-cold-and-distant-origin-of-the)[doi](https://doi.org/10.1038/s41586-026-10771-6)cited 6 times here**SRC** 0DFPWGSFXVMV
1. 7.[Roth, N., Cordiner, M., Milam, S. et al. 2026. An Enriched Methane D/H Ratio in the Interstellar Object 3I/ATLAS. Nature Astronomy.](https://mysteriesdept.com/sources/SRC0DFPWGSFZ0SM/an-enriched-methane-d-h-ratio-in-the-interstellar-object-3i)[doi](https://doi.org/10.1038/s41550-026-03002-5)cited 5 times here**SRC** 0DFPWGSFZ0SM
1. 8.[NASA/JPL Solar System Dynamics 2026. JPL Horizons ephemerides for 3I/ATLAS (solution JPL 55).](https://mysteriesdept.com/sources/SRC0DFPZ6F4PYM8/jpl-horizons-ephemerides-for-3i-atlas-solution-jpl-55)cited 5 times here**SRC** 0DFPZ6F4PYM8
1. 9.[Hibberd, A., Crowl, A., Loeb, A. 2025. Is the Interstellar Object 3I/ATLAS Alien Technology?. arXiv.](https://mysteriesdept.com/sources/SRC0CSKBET26693/is-the-interstellar-object-3i-atlas-alien-technology)cited 7 times here**SRC** 0CSKBET26693
1. 10.[Space.com 2025. NASA reveals new images of interstellar comet 3I/ATLAS from across the solar system: 'It looks and behaves like a comet'.](https://mysteriesdept.com/sources/SRC0DFPZ6F4QP03/nasa-reveals-new-images-of-interstellar-comet-3i-atlas-from)cited 3 times here**SRC** 0DFPZ6F4QP03
1. 11.[IAU Central Bureau for Astronomical Telegrams 2025. CBET 5578: Comet C/2025 N1 (ATLAS).](https://mysteriesdept.com/sources/SRC0DFPZ6F4HKRA/cbet-5578-comet-c-2025-n1-atlas)cited 3 times here**SRC** 0DFPZ6F4HKRA
1. 12.[Chandler, C., Bernardinelli, P., Jurić, M. et al. 2025. NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1). ApJL.](https://mysteriesdept.com/sources/SRC0DFPWGSEZJ1N/nsf-doe-vera-c-rubin-observatory-observations-of)[doi](https://doi.org/10.3847/2041-8213/ae4b3a)cited 1 time here**SRC** 0DFPWGSEZJ1N
1. 13.[Feinstein, A., Noonan, J., Seligman, D. 2025. Precovery Observations of 3I/ATLAS from TESS Suggests Possible Distant Activity. arXiv.](https://mysteriesdept.com/sources/SRC0DFPWGSF7RZR/precovery-observations-of-3i-atlas-from-tess-suggests)cited 2 times here**SRC** 0DFPWGSF7RZR
1. 14.[Ye, Q., Kelley, M., Hsieh, H. et al. 2025. Prediscovery Activity of New Interstellar Object 3I/ATLAS: A Dynamically-Old Comet? ApJL 993, L31.](https://mysteriesdept.com/sources/SRC0DFPWGSFC7BZ/prediscovery-activity-of-new-interstellar-object-3i-atlas-a)[doi](https://doi.org/10.3847/2041-8213/ae147b)cited 1 time here**SRC** 0DFPWGSFC7BZ
1. 15.[Lisse, C., Bach, Y., Crill, B. et al. 2025. SPHEREx Pre-Perihelion Mapping of H2O, CO2, and CO in Interstellar Object 3I/ATLAS. arXiv.](https://mysteriesdept.com/sources/SRC0DFPWGSFKWX5/spherex-pre-perihelion-mapping-of-h2o-co2-and-co-in)cited 3 times here**SRC** 0DFPWGSFKWX5
1. 16.[Jewitt, D., Hui, M., Mutchler, M. et al. 2025. Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS. arXiv.](https://mysteriesdept.com/sources/SRC0CSKBDK04FD6/hubble-space-telescope-observations-of-the-interstellar)[doi](https://doi.org/10.3847/2041-8213/adf8d8)cited 5 times here**SRC** 0CSKBDK04FD6
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1. 18.[ESA 2025. ESA's ExoMars and Mars Express observe comet 3I/ATLAS.](https://mysteriesdept.com/sources/SRC0DFPZ6F4QTND/esas-exomars-and-mars-express-observe-comet-3i-atlas)cited 2 times here**SRC** 0DFPZ6F4QTND
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Last edited 2 Nov 2026