Physical characterization and origin of binary near-Earth asteroid (175706) 1996 FG3

TL;DR

This study provides a detailed physical characterization of the binary near-Earth asteroid 1996 FG3, including size, albedo, and spectral type, and explores its likely origin in the inner main asteroid belt.

Contribution

It extends the physical understanding of 1996 FG3 with new infrared observations and refines its classification and origin hypotheses.

Findings

Derived system diameter of 1.90 km with low albedo of 0.039.

Spectral analysis suggests a B-type classification, consistent with primitive asteroid characteristics.

Possible origin in the inner main asteroid belt via specific resonances.

Abstract

The near-Earth asteroid (NEA) (175706) 1996 FG3 is a particularly interesting spacecraft target: a binary asteroid with a low-DeltaV heliocentric orbit. The orbit of its satellite has provided valuable information about its mass density while its albedo and colors suggest it is primitive or part of the C-complex taxonomic grouping. We extend the physical characterization of this object with new observations of its emission at mid-Infrared (IR) wavelengths and with near-IR reflection spectroscopy. We derive an area-equivalent system diameter of 1.90 \pm 0.28 km (corresponding to approximate component diameters of 1.83 km and 0.51 km, respectively) and a geometric albedo of 0.039 \pm 0.012. 1996 FG3 was previously classified as a C-type asteroid, though the combined 0.4--2.5 micron spectrum with thermal correction indicates classification as B-type; both are consistent with the low measured albedo. Dynamical studies show that 1996 FG3 has most probably originated in the inner main asteroid belt. Recent work has suggested the inner Main Belt (142) Polana family as the possible origin of another low-DeltaV B-type NEA, (101955) 1999 RQ36. A similar origin for 1996 FG3 would require delivery by the overlapping Jupiter 7:2 and Mars 5:9 mean motion resonances rather than the nu-6 resonance, and we find this to be a low probability, but possible, origin.