Determine whether pebbles survive ice melting and aqueous alteration

Determine whether pebbles can survive dissociation during ice melting in the undifferentiated region of Ryugu’s parent planetesimal, including whether cementation-like physicochemical processes can promote their solidification during ice melting and aqueous alteration.

Background

The thermal evolution model assumes that the pebble size within the differentiated core remains approximately equivalent to the pebble size in the solar protoplanetary disk. This assumption may fail if the original pebbles are disrupted when ice melts and aqueous alteration begins in the undifferentiated region.

The survival or modification of pebbles affects the inferred relationship between the modeled permeability of the pebble-pile core and the original pebble population. Resolving this issue is therefore important for interpreting the model-derived pebble-size constraint for Ryugu’s parent planetesimal.

References

Although it remains uncertain whether pebbles can survive dissociation during ice melting in the undifferentiated region, physicochemical processes akin to cementation may promote their solidification as ice melting and aqueous alteration proceed.

— Formation of Ryugu's parent planetesimal beyond the CO$_{2}$ snow line from small pebbles: insights from thermal evolution modeling  (2609.20608 - Arakawa et al., 17 Sep 2026) in Section 4.2, "Size and birthplace of Ryugu's parent planetesimal"