Impact melt
Impact melting is the result of hypervelocity impact events on the surface of a planetary body, causing whole-rock melting of the target rocks (the existing rocks beneath the impact site). Impact melts have been recognised from many terrestrial impact structures, such as the Sudbury and Chicxulub structures. Evidence of melting has also been found associated with many lunar impact structures such as Tycho[1] and Necho.[2] Impact melts have also been identified on Mars, Mercury[3] and Venus.[4]
Formation mechanism
[edit]Melting of the target rocks during an impact event is caused by the generation of waste heat energy during decompression after the initial high-pressure shock wave caused by the impact. This heat may lead to wholesale melting and vaporisation, although the ease with which this occurs is affected by the compressibility of the materials involved. The more compressible they are, the more likely they are to melt at any given shock pressure, as is demonstrated by the common occurrence of melted lunar regolith, while neighbouring crystalline rocks are not affected. Impact melting occurs as part of a highly dynamic process, with the melts produced moving rapidly into the transient cavity created by the impact.[3]
Impact melt products
[edit]The types of melt products produced by the impact will depend mainly on the amount of melt generated, its subsequent history within the impact structure, including the rate at which it cools. Rapid cooling of melts produces glass of two main types, mineral glasses, which have the composition of the minerals that they derive from, and rock glasses that represent the result of melting of the whole rock. Mineral glasses may be produced at grain contacts and have a mixed composition reflecting the minerals involved. Slower cooling, which allows mineral growth to occur, have similar textures to other igneous rocks.[3]
References
[edit]- ↑ Krüger, T.; van der Bogert, C.H.; Hiesinger, H. (2016). "Geomorphologic mapping of the lunar crater Tycho and its impact melt deposits". Icarus. 273: 164–181. doi:10.1016/j.icarus.2016.02.018.
- ↑ Hu, H.; Zeng, X.; Li, X.; Liu, J. (2025). "Lunar Highland Preserves Meteoritic-iron-rich Materials in the Earth–Moon System". The Astrophysical Journal. 993 (1). doi:10.3847/1538-4357/ae08b5.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - 1 2 3 Osinski, G.R.; Grieve, R.A.; Marion, C.; Chanou, A. (2013). "9. Impact melting". In Osinski, G.R.; Pierazzo, E. (eds.). Impact Cratering: Processes and Products. Wiley. pp. 125–145. ISBN 9781405198295.
- ↑ Borrelli, M.; Ganesh, I.; Bourg, L. (2026). "Emplacement of Venus' Crater Outflows as Impact Melt". Journal of Geophysical Research: Planets. 131 (8) e2026JE009826. doi:10.1029/2026JE009826.