[astro-ph.EP] We present the first spectroscopic mineralogical analysis of the dust coma of an interstellar object (ISO) from JWST mid-infrared spectroscopy of 3I/ATLAS (3I).
3I exhibits a strong 10-micron emissivity feature commonly seen on asteroids, comets, disks, and the interstellar medium. Characterization of this 10-micron emissivity maximum reveals that 3I’s dust composition is dominated by amorphous silicates, and that 3I is unlike Solar System comets, which show significant crystalline silicate dust. Instead, 3I’s dust composition is more similar to circumstellar transition disks and the interstellar medium.
We suggest 3I may have formed in a distant part of its home system out of interstellar medium-like material, without substantial incorporation of silicates condensed near its host star, unlike the mixing scenarios commonly hypothesized for Solar System comets.
Alternatively, 3I’s original crystalline silicates may have been amorphized during its Gyr-long journey, although we find this alternative less likely due to 3I’s mass loss rate and distinct 10 micron feature as opposed to observed Solar System comets.
Matthew Belyakov, Ian Wong, Carey M. Lisse, M. Ryleigh Davis, Bryce T. Bolin, Audrey Martin, Klaus M. Pontoppidan, Geoffrey A. Blake, Christine Chen, Michael E. Brown
Comments: 21 pages, 6 figures, submitted to ApJL
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2606.27535 [astro-ph.EP] (or arXiv:2606.27535v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2606.27535
Focus to learn more
Submission history
From: Matthew Belyakov
[v1] Thu, 25 Jun 2026 20:32:42 UTC (2,535 KB)
https://arxiv.org/abs/2606.27535
Astrobiology, Astrochemistry, Astrogeology,
