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This paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two‐stage light‐gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane‐driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high‐temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters.

Electron-impact ionization in a time-of-flight mass spectrometer of C(20)H(0-3)Br(14-12) probes-secured from C(20)H(20) dodecahedrane by a "brute-force" bromination protocol-provided bromine-free C(20)H(0-2(3)) anions in amounts that allowed the clean mass-separation of the hydrogen-free C(20) (-) ions and the photoelectron (PE) spectroscopic characterization as C(20) fullerene (electron affinity (EA)=2.25+/-0.03 eV, vibrational progressions of 730+/-70). The extremely strained C(20) fullerene ions surfaced as kinetically rather stable entities (lifetime of at least the total flight time of 0.4 ms); they only very sluggishly expel a C(2) unit. The HOMO and LUMO are suggested to be almost degenerate (DeltaE=0.27 eV). The assignment as a fullerene was corroborated by the PE characterization of the C(20) bowl (EA=2.17+/-0.03 eV, vibrational progression of 2060+/-50 cm(-1)) analogously generated from C(20)H(10) corannulene (C(20)H(1-3)Br(9-8) samples) and comparably stable. Highly resolved low-temperature PE spectra of the known C(20) ring (EA=2.49+/-0.03 eV, vibrational progressions 2022+/-45 and 455+/-30 cm(-1)), obtained from graphite, display an admixture of, most probably, a bicyclic isomer (EA=3.40+/-0.03 eV, vibrational progression 455+/-30 cm(-1)). The C(20) (+(-)) and C(20)H(2) (+(-)) cluster ions generated from polybrominated perylene (C(20)H(0-2)Br(12-10)) have (most probably) retained the planar perylene-type skeleton (sheet, EA=2.47+/-0.03 eV, vibrational progressions of 2089+/-30 and 492+/-30 cm(-1) and EA=2.18+/-0.03 eV, vibrational progressions of 2105+/-30 and 468+/-30 cm(-1)).

Abstract-Within the frame of the MEMIN research unit (Multidisciplinary Experimental and Numerical Impact Research Network), impact experiments on sandstone targets were carried out to systematically study the influence of projectile mass, velocity, and target water saturation on the cratering and ejection processes. The projectiles were accelerated with twostage light-gas guns (Ernst-Mach-Institute) onto fine-grained targets (Seeberger sandstone) with about 23% porosity. Collection of the ejecta on custom-designed catchers allowed determination of particle shape, size distribution, ejection angle, and microstructures. Mapping of the ejecta imprints on the catcher surface enabled linking of the different patterns to ejection stages observed on high-speed videos. The increase in projectile mass from 0.067 to 7.1 g correlates with an increase in the total ejected mass; ejecta angles, however, are similar in range for all experiments. The increase in projectile velocity from 2.5 to 5.1 km scorrelates with a total ejecta mass increase as well as in an increase in comminution efficiency, and a widening of the ejecta cone. A higher degree of water saturation of the target yields an increase in total ejecta mass up to 400% with respect to dry targets, higher ejecta velocity, and a steeper cone. These data, in turn, suggest that the reduced impedance contrast between the quartz grains of the target and the pores plays a primary role in the ejecta mass increase, while vaporization of water determines the ejecta behavior concerning ejecta velocity and particle distribution.