1132 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 36, NO. 4, AUGUST 2008 Laboratory Craters: Modeling Experiments for Meteorite Impact Craters? Tara Desai, Dimitri Batani, Marco Bussoli, Anna Maria Villa, Riccardo Dezulian, and Eduard Krousky Abstract—In this paper, we reveal the feasibility of obtaining laboratory craters to investigate planetary events such as mete- orite craters. Experiments were performed by using 0.44-μm laser beam with energy of ≤ 15 J in 350 ps (full-width at half-maximum) on aluminum targets. We obtain simple and complex craters similar in contour that are formed due to large meteorite impacts on the terrestrial surface. Simulations performed with the 2-D radiation hydrodynamic code MULTI help in understanding the origin of the experimentally observed central uplift of complex craters. Index Terms—Complex craters, laser ablation, laser produced craters, meteorite impact, shock pressure. A VIBRANT laboratory astrophysical research is emerging with intense lasers [1]. The important point is the possi- bility of scaling laboratory experiments to many astrophysical phenomena [2]. This also includes the possibility of extending the study of laboratory craters to meteorite impact craters. An effort to simulate micrometeorite impact on lunar rocks and lunar soil due to the analogy between the microparticle impact and the laser matter impact has been reported [3]. In one of our earlier works, we have shown that the extrapolation of the crater depths [4] obtained at low laser energies fits well with the depth produced in nuclear explosions [5]. Therefore, it seems that there is a universal scaling law governing crater formation. This can be justified because the hydrodynamic processes involved in crater formation take place on timescales much larger than laser pulse duration, and crater formation takes place on spatial scale lengths much larger than the laser focal spot. Therefore, the deposition of laser energy on target can be considered as taking place instantaneously at a given point source. Therefore, the process of crater formation will be rather insensitive to the precise details of the laser pulse duration. The same approximations can be considered to hold in meteorite impacts. However, experiments on meteorite impact using laser radiation not only show similarities but also several differences with meteorite impact craters on planets. These details are discussed in [6]. In this paper, we only discuss the possibility of laboratory applications of plasma science to natural astronomical events like meteorite impact. Manuscript received November 30, 2007; revised February 12, 2008. T. Desai, D. Batani, M. Bussoli, and R. Dezulian are with the Dipartimento di Fisica “G. Occhialini,” Università degli Studi di Milano—Bicocca, 20126 Milano, Italy (e-mail: tara.desai@mib.infn.it). A. M. Villa is with the Dipartimento di Biotecnologie e Bioscienze, Univer- sità degli Studi di Milano—Bicocca, 20126 Milano, Italy. E. Krousky is with the PALS Research Centre, 18221 Prague 8, Czech Republic. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPS.2008.926839 Fig. 1. Bowl-shaped simple crater. Diameter: ∼204 μm; depth: 35 μm. Present experiments were performed by using the Prague Astrix Iodine Gas Laser System at 0.44-μm wavelength (3ω of iodine laser) in 350-ps (full-width at half-maximum) duration. Aluminum targets of 100 μm thickness were placed in the vacuum chamber. Laser radiation was focused normal to the target surface, and spot diameter was ∼ 400 μm. A phase zone plate was used to smooth the laser beam to produce a flat-top intensity distribution in the focal spot. Laser energy was varied up to 15 J corresponding to an intensity range (8−30 × 10 12 W/cm 2 ). Experimental crater depth and diameter were measured by using laser scanning confocal microscope (LSCM) with mag- nification of ×800. LSCM images were obtained in reflection mode with a Leica TCS SP2 confocal microscope coupled to a DMIRE2-inverted microscope. Comparison with SEM results showed good agreement. We used the Leica LCS software for a 3-D reconstruction of crater topography. We have obtained several simple and complex craters in our experimental energy range. We have maintained nearly constant focal diameter. For low energies, we obtained simple craters, whereas in increasing the laser energy, we got several complex craters. Above 10 J, we obtained clear holes in 100-μm-thick aluminum target. Fig. 1 shows the image of simple bowl-shaped crater (diameter: ∼ 204 μm; depth: ∼ 35 μm). Simple craters varied from shallow to bowl shape depending on the laser energy. Fig. 2 shows the reconstructed 3-D image of a complex crater obtained with laser energy =6.14 J (I ∼ 10 13 W/cm 2 ) corresponding to a shock pressure of ∼ 4 Mbar on target. The image shows a crater with 520 μm diameter and 43 μm depth. Uplift has 82 μm diameter and is 40 μm high above the original surface. Fig. 3 shows another complex crater with ∼490 μm diameter and ∼ 60 μm depth obtained with 3.64-J energy (I = 7 × 10 12 W/cm 2 ). Fig. 3 is tilted to see internal structures. Thus, the laser energy seems to be one of the driving pa- rameter for obtaining central uplift in complex craters (for a 0093-3813/$25.00 © 2008 IEEE