4:00 PM - 4:15 PM
[PPS07-15] Dust growth process investigated by material strength of dust aggregates and by explorations of small Solar System bodies
Keywords:dust aggregates, tensile strength, compressive strength, comets, protoplanetary disks, planetesimals
How are planets formed? In planet formation theory, sub-micrometer-sized dust grains first grow into kilometer-sized planetesimals. The dust aggregates formed during this process are theoretically expected to have a very low density. However, astronomical observations by such as ALMA suggest that dust aggregates in protoplanetary disks are sub-millimeter-sized and have a high density. This means that some compaction processes are necessary for these dust aggregates, but it is not well understood. In this work, we focused on kilometer-sized objects in the Solar System. In particular, we focused on comets and asteroids, which are thought to be remnants of planetesimals, and investigated the dust growth process from comets and asteroids by using the material strength of dust aggregates.
In this work, we formulated the material strength of dust aggregates and applied it to comets and asteroids. First, we calculated and formulated the tensile and compressive strengths of dust aggregates by using numerical simulations that take into account the contact mechanics of dust particles. Next, we compared the tensile strength of dust aggregates with that of comets. Then, we calculated the bulk density and size of dust aggregates, which are determined by the balance between the compressive strength and the self-gravity, and compared them with those of comets and asteroids. As a result, these results indicate that comets can be explained by dust aggregates that consist of 1-µm-radius particles. This suggests that dust particles with a size of 1 µm are necessary for planet formation, rather than the previously assumed interstellar dust size of 0.1 µm. We also found that the self-gravity compression of planetesimals larger than 100 km in size is necessary for the formation of high-density dust aggregates observed by ALMA. This suggests that dust aggregates in protoplanetary disks are debris of planetesimals.
In this work, we formulated the material strength of dust aggregates and applied it to comets and asteroids. First, we calculated and formulated the tensile and compressive strengths of dust aggregates by using numerical simulations that take into account the contact mechanics of dust particles. Next, we compared the tensile strength of dust aggregates with that of comets. Then, we calculated the bulk density and size of dust aggregates, which are determined by the balance between the compressive strength and the self-gravity, and compared them with those of comets and asteroids. As a result, these results indicate that comets can be explained by dust aggregates that consist of 1-µm-radius particles. This suggests that dust particles with a size of 1 µm are necessary for planet formation, rather than the previously assumed interstellar dust size of 0.1 µm. We also found that the self-gravity compression of planetesimals larger than 100 km in size is necessary for the formation of high-density dust aggregates observed by ALMA. This suggests that dust aggregates in protoplanetary disks are debris of planetesimals.