Formation Process of Small Solar System Bodies Investigated by Material Strength of Dust Aggregates

Speaker: Misako Tatsuuma
(Univ. of Tokyo, *Student talk)


On the formation of small solar system bodies, there are many theories such as direct coagulation growth, pebble accretion, and some instabilities. To investigate the formation process, we focus on the material strength of these bodies. The internal density of bodies larger than several hundred meters is thought to be determined by the balance between self-gravity and compressive strength. In this work, we calculate the compressive strength of micron-sized dust aggregates by using dust N-body calculation. As a result, we succeeded in calculating the compressive strength of ice and silicate dust aggregates continuously from the volume filling factor of less than 0.1 to high density. Then, we calculate the internal density of the dust aggregates by assuming the balance between the self-gravity and compressive strength and compare it with the internal density of small solar system bodies. We found that the trans-Neptunian objects (TNOs) can be explained by ice dust aggregates, while comets including 67P/Churyumov-Gerasimenko can be explained by silicate dust aggregates. On the other hand, the densities of the asteroids Ryugu and Bennu are too dense to be explained by the dust aggregates in this work. To form such dense objects, it is necessary to form tens-kilometer-sized objects. In other words, we suggest that Ryugu and Bennu are collections of debris, and their parent bodies’ size is tens of kilometers or more.