Comets and Asteroids

Hunting for Hydrated Minerals on Trans-Neptunian Objects

By Keith Cowing
Status Report
December 20, 2023
Filed under , , , , , , , , , , ,
Hunting for Hydrated Minerals on Trans-Neptunian Objects
Optical reflectance spectra of 2004 GV9. Panel A: Here we compare our new GMOS reflectance spectra of 2004 GV9 both to each other and to coarse spectra derived from published single-epoch photometry (Rabinowitz et al. 2008; DeMeo et al. 2009; Fraser et al. 2015; Tegler et al. 2016). Hollow points in the GMOS spectra are either affected by incomplete background subtraction, telluric band residuals, proximity to the GMOS chip gaps, or a combination of these effects. All datasets are scaled to unit reflectance at 0.625 µm. We present all spectra calibrated with HD 124523 overlaid for direct comparison, and also offset for clarity. All offset spectra are offset vertically in increments of +0.2. Panel B: Here we show our 2004 GV9 spectra following division by a line fitted to them across their full wavelength coverage. Spectra from each epoch are offset vertically for clarity in increments of +0.1. Only spectra calibrated with HD 124523 are shown. Points affected by residuals of telluric absorption or imperfect background subtraction have been omitted. — astro-ph.EP

We present new optical reflectance spectra of three potentially silicate-rich Trans-Neptunian Objects (TNOs). These spectra were obtained with the aim of confirming past hints and detections of 0.7 micron absorption features associated with the presence of iron-bearing phyllosilicates.

Our new spectrum of 120216 (2004 EW95) presents clearly detected absorption features that are similar in shape to hydrated mineral absorption bands present in the spectra of aqueously altered outer-main belt asteroids. Four new reflectance spectra of 208996 (2003 AZ84) obtained at separate epochs all appear featureless, but vary significantly in spectral gradient (between approximately 3.5 %/0.1 micron and 8.5 %/0.1 micron) on a timescale consistent with this object’s nominal rotational period.

We report the first four optical reflectance spectra of 90568 (2004 GV9), finding them all to be featureless but consistent with colors previously reported for this object. We speculate that impacts are the only mechanism capable of delivering, excavating, or forming hydrated minerals at the surfaces of TNOs in detectable concentrations; as a result, any deposits of hydrated minerals on TNOs are predicted to be localized and associated with impact sites.

Globally altered TNOs (as observationally suggested for 2004 EW95) plausibly formed more easily at smaller heliocentric distances (< 15 au) before being transplanted into the current Trans-Neptunian population.

Tom Seccull, Wesley C. Fraser, Dominik A. Kiersz, Thomas H. Puzia

Comments: 25 pages, 7 figures, 6 tables, accepted for publication in PSJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2312.11646 [astro-ph.EP] (or arXiv:2312.11646v1 [astro-ph.EP] for this version)
Submission history
From: Tom Seccull
[v1] Mon, 18 Dec 2023 19:01:21 UTC (1,643 KB)
Astrobiology, Astrochemistry,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻