Physical Characterization of Metal-rich Near-Earth Asteroids 6178 (1986 DA) and 2016 ED85

TL;DR

This study provides near-infrared spectral analysis of two metal-rich near-Earth asteroids, revealing their composition, origin, and potential meteorite analogs, and suggests they contain significant metal reserves.

Contribution

It offers the first detailed compositional analysis of NEAs 6178 (1986 DA) and 2016 ED85, highlighting their metal-rich nature and potential resource value.

Findings

Spectral characteristics indicate metal-rich composition with weak pyroxene absorption.

Asteroids likely transported via 5:2 resonance with Jupiter.

Potential for substantial metal reserves exceeding global supplies.

Abstract

Metal-rich near-Earth asteroids (NEAs) represent a small fraction of the NEA population that is mostly dominated by S- and C-type asteroids. Because of this, their identification and study provide us with a unique opportunity to learn more about the formation and evolution of this particular type of bodies, as well as their relationship with meteorites found on Earth. We present near-infrared (NIR) spectroscopic data of NEAs 6178 (1986 DA) and 2016 ED85. We found that the spectral characteristics of these objects are consistent with those of metal-rich asteroids, showing red slopes, convex shapes, and a weak pyroxene absorption band at $\sim$0.93 $\mu$m. The compositional analysis showed that they have a pyroxene chemistry of Fs$_{40.6\pm3.3}$Wo$_{8.9\pm1.1}$ and a mineral abundance of $\sim$15% pyroxene and 85% metal. We determined that these objects were likely transported to the near-Earth space via the 5:2 mean motion resonance with Jupiter. Asteroid spectra were compared with the spectra of mesosiderites and bencubbinites. Differences in the NIR spectra and pyroxene chemistry suggest that bencubbinites are not good meteorite analogs. Mesosiderites were found to have a similar pyroxene chemistry and produced a good spectral match when metal was added to the silicate component. We estimated that the amounts of Fe, Ni, Co, and the platinum group metals present in 1986 DA could exceed the reserves worldwide.