Searching for the Cradle of L Chondrites on (20) Massalia's Surface

We recently proposed that the Massalia asteroid family is the source of the most common meteorites found on Earth: the ordinary L chondrites (Marsset, Vernazza, Brož et al. 2024, Nature). This hypothesis is supported by several lines of evidence:
(1) spectral similarities between Massalia family members and L chondrites;
(2) the family’s steep size-frequency distribution, extending down to the detection limit of current all-sky surveys, indicating a large population of small fragments;
(3) the orbital clustering of L-chondrite-like Near-Earth Objects (NEOs) near the family and the 3:1 mean-motion resonance with Jupiter;
(4) the presence of a zodiacal dust band intersecting the family, suggesting ongoing dust production that feeds the inner Solar System;
(5) the dynamical and collisional ages of the family, which we found to be consistent with the argon isotope ages measured in L chondrites;
and (6) the reconstructed pre-atmospheric orbits of L chondrites, pointing to a low-inclination source in the inner asteroid belt.

In our initial study, we made several testable predictions for future large-scale surveys (e.g., LSST) and targeted observations to further validate our finding. One such prediction was the existence of a large impact crater on (20) Massalia itself. Here, we present high-resolution adaptive optics (AO) images of Massalia obtained with VLT/SPHERE to test this prediction. By combining these multi-epoch AO observations covering a full rotation with optical light curves , we determined the asteroid’s spin orientation and derived a detailed shape model. Additionally, we analyzed an extensive set of thermal measurements to estimate (20) Massalia’s thermal inertia and surface roughness. We will discuss these results in the context of the proposed link between the Massalia family and L chondrites.