Rotational properties of Maria asteroid family

TL;DR

This study investigates the rotational properties of the Maria asteroid family, revealing a non-Maxwellian spin rate distribution influenced by non-gravitational forces and a predominance of prograde rotators, with implications for NEA delivery.

Contribution

It provides new rotational period measurements for 34 Maria family asteroids and analyzes their spin orientations, highlighting the influence of the YORP effect and resonance-driven ejections.

Findings

Significant excess of fast and slow rotators in the distribution.

Non-Maxwellian spin rate distribution confirmed at 92% confidence.

Prograde spins outnumber retrograde spins by 3 to 1.

Abstract

Maria family is regarded as an old-type (~3 +/- 1 Gyr) asteroid family which has experienced substantial collisional and dynamical evolution in the Main-belt. It is located nearby the 3:1 Jupter mean motion resonance area that supplies Near-Earth asteroids (NEAs) to the inner Solar System. We carried out observations of Maria family asteroids during 134 nights from 2008 July to 2013 May, and derived synodic rotational periods for 51 objects, including newly obtained periods of 34 asteroids. We found that there is a significant excess of fast and slow rotators in observed rotation rate distribution. The two-sample Kolmogorov-Smirnov test confirms that the spin rate distribution is not consistent with a Maxwellian at a 92% confidence level. From correlations among rotational periods, amplitudes of lightcurves, and sizes, we conclude that the rotational properties of Maria family asteroids have been changed considerably by non-gravitational forces such as the YORP effect. Using a lightcurve inversion method (Kaasalainen & Torppa 2001; Kaasalainen et al. 2001), we successfully determined the pole orientations for 13 Maria members, and found an excess of prograde versus retrograde spins with a ratio (N_p/N_r) of 3. This implies that the retrograde rotators could have been ejected by the 3:1 resonance into the inner Solar System since the formation of Maria family. We estimate that approximately 37 to 75 Maria family asteroids larger than 1 km have entered the near-Earth space every 100 Myr.