Physical Characterization of ~2-meter Diameter Near-Earth Asteroid 2015 TC25: A possible boulder from E-type Asteroid (44) Nysa

TL;DR

This study provides a detailed physical characterization of the small (~2-meter) near-Earth asteroid 2015 TC25, revealing its composition, rapid rotation, and likely origin from the inner main belt asteroid (44) Nysa.

Contribution

It is the first detailed physical analysis of such a small NEA, combining optical, infrared, and radar data to determine its composition, size, and potential source body.

Findings

2015 TC25 has a high albedo similar to aubrites.

It is a very fast rotator with a 133-second period.

Spectral analysis links it to asteroid (44) Nysa.

Abstract

Small near-Earth asteroids (>20 meters) are interesting because they are progenitors for meteorites in our terrestrial collection. Crucial to our understanding of the effectiveness of our atmosphere in filtering low-strength impactors is the physical characteristics of these small near-Earth asteroids (NEAs). In the past, characterization of small NEAs has been a challenge because of the difficulty in detecting them prior to close Earth flyby. In this study we physically characterized the 2-meter diameter near-Earth asteroid 2015 TC25 using ground-based optical, near-infrared and radar assets during a close flyby of the Earth (distance 69,000 miles) in Oct. 2015. Our observations suggest that its surface composition is similar to aubrites, a rare class of high albedo differentiated meteorites. Aubrites make up only 0.14 % of all know meteorites in our terrestrial meteorite collection. 2015 TC25 is also a very fast rotator with a rotation period of 133 seconds. We compared spectral and dynamical properties of 2015 TC25 and found the best candidate source body in the inner main belt to be the 70-km diameter E-type asteroid (44) Nysa. We attribute difference in spectral slope between the two objects to the lack of regolith on the surface of 2015 TC25. Using the albedo of E-type asteroids (50-60%) we refine the diameter of 2015 TC25 to 2-meters making it one of the smallest NEA ever to be characterized.