Hypervelocity impacts in the laboratory on hot rock targets

The variation of impact crater size in rock has been investigated as a function of target temperature in the range 150 K - 1150 K. Three rock types were used: limestone, sandstone and basalt. A total of thirty impacts were observed, at a typical impact speed of 5 km s(-1) with a 0.8 mm diameter stainless steel spherical projectile. The three rocks behaved in two ways. The craters in limestone and sandstone initially grew in size, until a maximum was reached at around 500 K. Crater size then fell again as temperature increased further. For basalt however, crater size fell as temperature increased, reaching a constant level above 800 K. This strongly suggests that crater sizes seen in experiments on Earth, should not be taken as typical, rather they are a function of rock temperature. It proved difficult to relate crater size to target strength, as data in the literature on rock strength vs. temperature were in some cases contradictory. (C) 2017 The Authors. Published by Elsevier Ltd.