Detection of Water and/or Hydroxyl on Asteroid (16) Psyche

TL;DR

This study detected a hydration feature on asteroid Psyche using infrared spectroscopy, indicating the presence of water or hydroxyl, which suggests surface heterogeneity and implications for its composition.

Contribution

First detection of a 3 micron hydration absorption feature on asteroid Psyche, revealing surface heterogeneity and challenging the view of it being purely metallic.

Findings

Psyche exhibits a 3 micron hydration absorption band.

Surface heterogeneity in metal/silicate ratio observed.

Implications for Psyche's composition and history.

Abstract

In order to search for evidence of hydration on M-type asteroid (16) Psyche, we observed this object in the 3 micron spectral region using the long-wavelength cross-dispersed (LXD: 1.9-4.2 micron) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). Our observations show that Psyche exhibits a 3 micron absorption feature, attributed to water or hydroxyl. The 3 micron absorption feature is consistent with the hydration features found on the surfaces of water-rich asteroids, attributed to OH- and/or H2O-bearing phases (phyllosilicates). The detection of a 3 micron hydration absorption band on Psyche suggests that this asteroid may not be metallic core, or it could be a metallic core that has been impacted by carbonaceous material over the past 4.5 Gyr. Our results also indicate rotational spectral variations, which we suggest reflect heterogeneity in the metal/silicate ratio on the surface of Psyche.