Near-infrared observations of active asteroid (3200) Phaethon reveal no evidence for hydration

Driss Takir,Tomoko Arai,Andrew S Rivkin,Joshua P Emery,Vishnu Reddy,Josef Hanuš,Theodore Kareta,Ellen S Howell

doi:10.1038/s41467-020-15637-7

Abstract

Asteroid (3200) Phaethon is an active near-Earth asteroid and the parent body of the Geminid Meteor Shower. Because of its small perihelion distance, Phaethon’s surface reaches temperatures sufficient to destabilize hydrated materials. We conducted rotationally resolved spectroscopic observations of this asteroid, mostly covering the northern hemisphere and the equatorial region, beyond 2.5-µm to search for evidence of hydration on its surface. Here we show that the observed part of Phaethon does not exhibit the 3-µm hydrated mineral absorption (within 2σ). These observations suggest that Phaethon’s modern activity is not due to volatile sublimation or devolatilization of phyllosilicates on its surface. It is possible that the observed part of Phaethon was originally hydrated and has since lost volatiles from its surface via dehydration, supporting its connection to the Pallas family, or it was formed from anhydrous material.

Highlights

Asteroid (3200) Phaethon is an active near-Earth asteroid and the parent body of the Geminid Meteor Shower
It is unlikely for water ice to survive and the dust to be ejected from Phaethon via gas drag from ice sublimation because this asteroid’s small perihelion distance and high temperature make ice unstable on even very short timescales[3]
Was found to be dynamically similar to Phaethon, and both asteroids are thought to be fragments generated by the breakup of a primitive precursor object[5]

Summary

Introduction

Asteroid (3200) Phaethon is an active near-Earth asteroid and the parent body of the Geminid Meteor Shower. We show that the observed part of Phaethon does not exhibit the 3-μm hydrated mineral absorption (within 2σ) These observations suggest that Phaethon’s modern activity is not due to volatile sublimation or devolatilization of phyllosilicates on its surface. 1234567890():,; Asteroid (3200) Phaethon is an Apollo-type near-Earth asteroid (NEA) that is thought to be the parent body of Geminid Meteor Stream[1]. While originally suggested to be inactive, Phaethon develops a small dust tail for a few days after its perihelion[2,3] The origin of this dust tail could be due to the desiccation and thermal breakdown of the surface[2] or the last gasps of a comet-like sublimation-driven activity[4].

Methods

Results

Conclusion