The fate of icy pebbles undergoing sublimation in protoplanetary discs

TL;DR

This study investigates the conditions under which icy pebbles in protoplanetary discs can survive sublimation without disruption, using experimental models to understand their potential role in planet formation near the water ice line.

Contribution

The paper presents experimental models showing that icy pebbles can survive sublimation under specific conditions, challenging previous assumptions about their disruption during sublimation.

Findings

Small silicate particles (<50um) help preserve pebbles during sublimation.

A small ice fraction (~15%) is optimal for pebble preservation.

Pebbles with coarse dust do not disrupt if small grains are present.

Abstract

Icy pebbles may play an important role in planet formation close to the water ice line of protoplanetary discs. There, dust coagulation is more efficient and re-condensation of vapor on pebbles may enhance their growth outside the ice line. Previous theoretical studies showed that disruption of icy pebbles due to sublimation increases the growth rate of pebbles inside and outside the ice line, by freeing small silicate particles back in the dust reservoir of the disc. However, since planet accretion is dependent on the Stokes number of the accreting pebbles, the growth of planetesimals could be enhanced downstream of the ice line if pebbles are not disrupting upon sublimation. We developed two experimental models of icy pebbles using different silicate dusts, and we exposed them to low-temperature and low-pressure conditions in a vacuum chamber. Increasing the temperature inside the chamber, we studied the conditions for which pebbles are preserved through sublimation without disrupting. We find that small silicate particles ($<50$um) and a small quantity of ice (around $15$% pebble mass) are optimal conditions for preserving pebbles through sublimation. Furthermore, pebbles with coarse dust distribution ($100-300$um) do not disrupt if a small percentage ($10-20$% mass) of dust grains are smaller than $50$um. Our findings highlight how sublimation is not necessarily causing disruption, and that pebbles seem to survive fast sublimation processes effectively.