Restitution coefficients and sticking velocities of a chondrule analogue colliding on a porous silica layer at impact velocities between 0.1 and 80 m s?1 |
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| Authors: | Yo-ichiro Uchiyama Masahiko Arakawa Chisato Okamoto Minami Yasui |
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| Institution: | 1. Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan;2. Graduate School of Science, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan;3. Japan Aerospace Exploration Agency, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara 252-5210, Japan;4. Organization of Advanced Science and Technology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan |
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| Abstract: | To study the accretional growth of rimmed chondrules and their agglomerates in the solar nebula, we measured the restitution coefficients, ε, and the sticking velocities to a porous silica layer, vc, by impacting the silica layer with a glass ball at velocities from 0.1 to 80 m s?1. We used a porous silica layer covering a basalt block with thicknesses ranging from 1/5 of the glass ball radius to equal to the glass ball radius as a rimmed chondrule analogue, and the porosity of the silica layer was set to be 70%, 80%, 85%, and 90%. Collisional experiments were conducted by means of the free fall method or by the use of a spring gun or a gas gun, allowing us to vary the impact velocity. We used a laser displacement meter to estimate the impact and rebound velocities as well as the acceleration during the collision at impact velocities below 1 m s?1. As a result, the sticking velocity, vc, of 90%- and 85%- porosity layers with a thickness equal to 1/2 of the glass ball diameter was 0.44 and 2.4 m s?1, respectively. On the other hand, we found a distinct barrier to sticking for smaller-porosity layers: the silicate layer with a porosity smaller than 80% never exhibited sticking at any impact velocity below 1 m s?1. Instead, we observed a rebound effect with restitution coefficients larger than 0.2. In the case of a silica layer with a porosity smaller than 80%, we observed the sub-sticking condition defined by ε < 0.1 at velocities extending from 5 m s?1 to 70 m s?1. |
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