Presentation Information
[PPS04-P03]Experiments on Impact-Induced Brecciation of Simulated Regolith and Strength Measurement of the Products
*Yuto Uno1, Koske Matsubara1, Akiko Nakamura1, Sunao Hasegawa2 (1.Kobe University, Graduate School of Science, Department of Planetology, 2.JAXA)
Keywords:
breccia,tensile strength,impact experiments,regolith
Most meteorites are formed by hypervelocity impacts on asteroid surfaces. This process induces shock metamorphism depending on the absorbed impact energy. This study focuses on brecciation, the process by which angular fragments formed by impacts consolidate into breccias. Brecciation is observed in many meteorites and is considered a crucial factor in investigating the surface evolution of asteroids. This study reproduces the formation process of brecciated meteorites through impact experiments. It also measures the strength of the resulting products and compares their strengths with those of actual meteorites.
The impact experiments were conducted using the two-stage light-gas gun at the Institute of Space and Astronautical Science. Targets consisted of silica sand with particle sizes of 1.5 µm and 63 µm. Projectiles comprised stainless steel and basalt with diameters of approximately 3 mm were fired four times at a velocity of approximately 4.4 km/s. The target was packed into a cylindrical container measuring 4.4 cm in inner diameter and 5 cm in height, suspended from above using fishing line and aligned with the projectile trajectory, and subjected to impact. The impact process was recorded using a high-speed camera and a flash X-ray device to capture the instant of impact and the compaction process within the container. Strength measurements of the resulting products recovered after impact were performed using a compression testing machine at Kobe University. The products obtained in this study are irregularly shaped and as small as a millimeter in size. Therefore, strength was measured using a point-load splitting tensile test with a custom fixture. To verify the validity of this method, splitting tensile tests and point-load splitting tensile tests were also performed on dihydrate gypsum of various sizes. Considering the size dependence of strength described by Weibull model, the results from the two methods were compared, revealing that the trends in size dependence were generally consistent.
As a result, two products (Sample A and B) were obtained in this study. SEM/EDS analysis revealed that Sample A consists of stainless steel and silica sand (63 µm), while Sample B consists of basalt and silica sand (1.5 µm), indicating that the target material adhered to the projectile material. Tensile strength measurements yielded values of 1.6 MPa for A and 2.2 MPa for B. When these values are extrapolated to the size of meteorites assuming a Weibull model, they are considered to be lower than those of actual meteorites. However, since the composition and size of the target and projectile materials in this study differ from those of actual asteroids, further experiments under different conditions are necessary.
This work was supported by the Hypervelocity Impact facility at ISAS, JAXA.
The impact experiments were conducted using the two-stage light-gas gun at the Institute of Space and Astronautical Science. Targets consisted of silica sand with particle sizes of 1.5 µm and 63 µm. Projectiles comprised stainless steel and basalt with diameters of approximately 3 mm were fired four times at a velocity of approximately 4.4 km/s. The target was packed into a cylindrical container measuring 4.4 cm in inner diameter and 5 cm in height, suspended from above using fishing line and aligned with the projectile trajectory, and subjected to impact. The impact process was recorded using a high-speed camera and a flash X-ray device to capture the instant of impact and the compaction process within the container. Strength measurements of the resulting products recovered after impact were performed using a compression testing machine at Kobe University. The products obtained in this study are irregularly shaped and as small as a millimeter in size. Therefore, strength was measured using a point-load splitting tensile test with a custom fixture. To verify the validity of this method, splitting tensile tests and point-load splitting tensile tests were also performed on dihydrate gypsum of various sizes. Considering the size dependence of strength described by Weibull model, the results from the two methods were compared, revealing that the trends in size dependence were generally consistent.
As a result, two products (Sample A and B) were obtained in this study. SEM/EDS analysis revealed that Sample A consists of stainless steel and silica sand (63 µm), while Sample B consists of basalt and silica sand (1.5 µm), indicating that the target material adhered to the projectile material. Tensile strength measurements yielded values of 1.6 MPa for A and 2.2 MPa for B. When these values are extrapolated to the size of meteorites assuming a Weibull model, they are considered to be lower than those of actual meteorites. However, since the composition and size of the target and projectile materials in this study differ from those of actual asteroids, further experiments under different conditions are necessary.
This work was supported by the Hypervelocity Impact facility at ISAS, JAXA.