# Detection of Rotational Spectral Variation on the M-type asteroid (16) Psyche

## TL;DR

This study combines multi-wavelength spectral data and shape models to analyze rotational spectral variations on asteroid (16) Psyche, revealing compositional heterogeneity and complex evolutionary history.

## Contribution

It provides the first comprehensive rotationally resolved NIR spectral analysis of Psyche integrating shape models and spectral calibration.

## Key findings

- Pyroxene band center varies from 0.92 to 0.94 microns.
- Average orthopyroxene content estimated at 6% ± 1%.
- Mass-deficit region shows highest radar albedo and spectral slope.

## Abstract

The asteroid (16) Psyche is of scientific interest because it contains ~ 1% of the total mass of the asteroid belt and is thought to be the remnant metallic core of a protoplanet. Radar observations have indicated the significant presence of metal on the surface with a small percentage of silicates. Prior ground-based observations showed rotational variations in the near-infrared (NIR) spectra and radar albedo of this asteroid. However, no comprehensive study that combines multi-wavelength data has been conducted so far. Here we present rotationally resolved NIR spectra (0.7-2.5 microns) of (16) Psyche obtained with the NASA Infrared Telescope Facility. These data have been combined with shape models of the asteroid for each rotation phase. Spectral band parameters extracted from the NIR spectra show that the pyroxene band center varies from ~ 0.92 to 0.94 microns. Band center values were used to calculate the pyroxene chemistry of the asteroid, whose average value was found to be Fs30En65Wo5. Variations in the band depth were also observed, with values ranging from 1.0 to 1.5%. Using a new laboratory spectral calibration we estimated an average orthopyroxene content of 6+/-1%. The mass-deficit region of Psyche, which exhibits the highest radar albedo, also shows the highest value for spectral slope and the minimum band depth. The spectral characteristics of Psyche suggest that its parent body did not have the typical structure expected for a differentiated body or that the sequence of events that led to its current state was more complex than previously thought.