Department of Earth Sciences

The near-Earth asteroids (162173) Ryugu, (25143) Itokawa, and (101955) Bennu are “rubble piles,” i.e., agglomerates of rocky fragments loosely held together by gravity, and all three are less than 1 km in diameter. The surfaces of these asteroids are covered with rocks ranging in size from decimeters to meters. Fine particles and dust are rare. The processes that could be responsible for the absence of dust on these asteroids are currently still poorly understood. In this project, we want to systematically investigate various processes using Ryugu as an example. Using infrared data from the Hayabusa2 mission, we estimate the maximum amount of dust that can be retained on the surface. Through numerical simulation of the plasma environment around Ryugu, we simulate and estimate whether dust particles on Ryugu can be charged and removed from the surface by photoemission and interaction with the solar wind. This process is often cited as the reason for the absence of dust on Ryugu, but has not yet been investigated for Ryugu. We are also using thermophysical models to investigate the structure of the asteroid material in order to estimate how the rocks on Ryugu react to micrometeorite impacts and thermal stresses and how these processes affect dust production. Answering the question of why so little dust and fine regolith was found on Ryugu is important in order to draw conclusions about the asteroid's formation in the early solar system from its current observable state.