The low surface thermal inertia of the rapidly rotating near-Earth asteroid 2016 GE1

Abstract

Asteroids smaller than about 100 meters are observed to rotate very fast, with periods often much shorter than the critical limit of 2.2 h. Some of these super-fast rotators can also achieve a very large semi-major axis drift induced by the Yarkovsky effect, that in turn, is determined by internal and surface physical properties. We consider the small super-fast rotating near-Earth asteroid 2016 GE1. This object rotates in just 34 seconds, and a large Yarkovsky effect has been determined from astrometry. Here we aim to constrain the thermal inertia of the surface of this extreme object. We used a recently developed statistical method to determine the thermal properties of near-Earth asteroids. The method is based on the comparison between the observed and the modelled Yarkovsky effect, and the thermal conductivity (inertia) is determined by a Monte Carlo approach. Parameters of the Yarkovsky effect model are either fixed if their uncertainty is negligible, modelled with a Gaussian distribution of the errors if they are measured, or deduced from general properties of the population of near-Earth asteroids when they are unknown. Using a well-established orbit determination procedure, we determined the Yarkovsky effect on 2016 GE1, and verified a significant semi-major axis drift rate. Using a statistical method, we showed that this semi-major axis drift rate could be explained only by low thermal inertia values below 100 J m${}^{-2}$ K${}^{-1}$ s${}^{-1/2}$: namely, 90\% of the probability density function of the model outcomes is contained at values smaller than 100 J m${}^{-2}$ K${}^{-1}$ s${}^{-1/2}$. We propose two possible interpretations for the extremely low values: a high porosity or a cracked surface, or a thin layer of fine regolith on the surface. Though this seems unexpected in either case, it opens up the possibility of a subclass of low thermal inertia, super-fast rotating asteroids.

Accepted for publication on A&A

References in corpus (11)

• Thermal inertia of near-Earth asteroids and implications for the magnitude of the Yarkovsky effect
• The thermal, mechanical, structural, and dielectric properties of cometary nuclei after Rosetta
• Hayabusa2 Extended Mission: New Voyage to Rendezvous with a Small Asteroid Rotating with a Short Period
• Debiased albedo distribution for Near Earth Objects
• SsODNet: The Solar system Open Database Network
• Physical characterisation of near-Earth asteroid (1620) Geographos. Reconciling radar and thermal-infrared observations
• Thermal Tomography of Asteroid Surface Structure
• Critical spin periods of sub-km-sized cohesive rubble-pile asteroids: dependencies on material parameters
• Low thermal conductivity of the superfast rotator (499998) 2011 PT
• Thermal properties of slowly rotating asteroids: Results from a targeted survey
• Thermal properties of large main-belt asteroids observed by Herschel PACS

Cited by in corpus (5)

• JWST sighting of decameter main-belt asteroids and view on meteorite sources
• Astrometry, orbit determination, and thermal inertia of the Tianwen-2 target asteroid (469219) Kamo`oalewa
• Rotation state, colors, and albedo of the mission-accessible tiny near-Earth asteroid 2001 QJ${}_{142}$
• ASTERIA -- Thermal Inertia Evaluation of asteroid Didymos
• Numerical Validation of the Yarkovsky Effect in Super-Fast Rotating Asteroids