Impact experiments with a new technique for acceleration of projectiles to velocities higher than Earthʼ s escape velocity of 11.2 km/s

• Published in: Journal of Geophysical Research. E. Planets Vol. 115; no. E04
• Main Authors: Kadono, T, Sakaiya, T, Hironaka, Y, Otani, K, Sano, T, Fujiwara, T, Mochiyama, T, Kurosawa, K, Sugita, S, Sekine, Y0, Nishikanbara, W1, Matsui, T2, Ohno, S3, Shiroshita, A4, Miyanishi, K5, Ozaki, N6, Kodama, R7, Nakamura, AM8, Arakawa, M9, Fujioka, S00, Shigemori, K01
• Format: Journal Article
• Language: English
• Published: 01-04-2010
• DOI: 10.1029/2009JE003385
• ISSN: 0148-0227

The impact velocities of asteroids on Earth and other terrestrial planets can be greater than 10 km/s, and impacts at these high velocities can produce significant effects on the planetary surfaces. However, since macroscopic (>~0.1 mm) projectiles with an aspect ratio of ~1 are not easily accelerated to more than 10 km/s in laboratories, there are few detailed experimental studies. In this paper, we demonstrate that impact velocities greater than 10 km/s can be achieved with glass and aluminum projectiles of 0.1-0.3 mm in diameter using a high-power laser, GEKKO XII-HIPER at Institute of Laser Engineering, Osaka University. The velocity of the projectiles is estimated based on the images taken by high-speed X-ray streak and framing cameras. Projectiles collide into copper or LiF plate targets. The copper plates are recovered for analysis. The sizes of craters on the copper plates are not far from the extrapolations from previous work with lower velocities. A tantalum witness plate placed near the copper plates records a large number of secondary craters from each impact. In the case of the impacts of the LiF plates, we observe two emission lines of Li gas using a spectrometer with a streak camera. Thus, we can simulate the hypervelocity impacts with velocities higher than 10 km/s in laboratories.