Impact experiments in low-temperature ice

New results of low-velocity impact experiments in cubic and cylindrical (20 cm) water-ice targets initially at 257 and 81 °K are reported. Impact velocities and impact energies vary between 0.1 and 0.64 km/sec and 10^9 and 10^(10) ergs, respectively. Observed crater diameters range from 7 to 15 cm and are two to three times larger than values found for equal-energy impacts in basaltic targets. Crater dimensions in ice targets increase slightly with increasing target temperatures. Crater volumes of strength-controlled ice craters are about 10 to 100 times larger than those observed for craters in crystalline rocks. Based on similarity analysis, general scaling laws for strength-controlled crater formation are derived and are applied to crater formation on the icy Galilean and Saturnian satellites. This analysis indicates that surface ages, based on impact-crater statistics on an icy crust, will appear greater than those for a silicate crust which experienced the same impact history. The greater ejecta volume for cratering in ice versus cratering in silicate targets leads to accelerated regolith production on an icy planet.

[1]  Y. Takagi,et al.  Cratering experiments in sands and a trial for general scaling law , 1983 .

[2]  R. Clark,et al.  Implications of using broadband photometry for compositional remote sensing of icy objects , 1982 .

[3]  D. Matson,et al.  Water ice polymorphs and their significance on planetary surfaces , 1980 .

[4]  V. R. Parameswaran,et al.  Brittle Fracture of Ice at 77 K , 1975, Journal of Glaciology.

[5]  E. M. Shoemaker,et al.  Craters and basins on Ganymede and Callisto - Morphological indicators of crustal evolution , 1982 .

[6]  J. B. Plescia,et al.  The geology of Ganymede , 1979 .

[7]  K. A. Holsapple,et al.  On the Scaling of Crater Dimensions 2. Impact Processes , 1982 .

[8]  Y. Takagi,et al.  Impact experiments on ice , 1983 .

[9]  S. K. Croft,et al.  Low-velocity impact craters in ice and ice-saturated sand with implications for Martian crater count ages. , 1979 .

[10]  Experimental hypervelocity impact into quartz sand. II - Effects of gravitational acceleration , 1977 .

[11]  T. Ahrens,et al.  The dynamic tensile strength of ice and ice‐silicate mixtures , 1983 .

[12]  K. Holsapple,et al.  Crater ejecta scaling laws - Fundamental forms based on dimensional analysis , 1983 .

[13]  D. Gault,et al.  Some comparisons of impact craters on Mercury and the Moon , 1975 .

[14]  T V Johnson,et al.  The Galilean Satellites and Jupiter: Voyager 2 Imaging Science Results , 1979, Science.

[15]  F. Hörz.  Structural and mineralogical evaluation of an experimentally produced impact crater in granite , 1969 .

[16]  Donald E. Gault,et al.  Displaced mass, depth, diameter, and effects of oblique trajectories for impact craters formed in dense crystalline rocks , 1973 .

[17]  T V Johnson,et al.  Encounter with saturn: voyager 1 imaging science results. , 1981, Science.

[18]  T. Ahrens,et al.  Fragmentation of ice by low velocity impact , 1982 .