Synonyms
Definition
Spallation zones are regions adjacent to the free surface of a solid where the reflection of a strong incident stress wave induces tensile stresses and ejects material at high speed. The tensile stresses add to the compressive stresses in the incident wave and partially cancel its compression, leading to high-speed ejection of lightly compressed (“shocked”) material.
History
Spallation of the surface following impingement of a strong shock wave was first observed in association with underground nuclear explosions. During the 1980s, accumulated evidence indicated that the SNC suite of meteorites originated on a large planet, probably Mars. Their launch raised the conundrum of how intact rocks could be ejected at high enough speed to escape from Mars (a minimum of 5 km/s) and yet escape melting or vaporization. Melosh (1984) first suggested that spallation could provide the answer. Furthermore, Melosh (1988)...
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References and Further Reading
Fajardo-Cavazos P, Langenhorst F, Melosh HJ, Nicholson WL (2009) Bacterial spores in granite survive hypervelocity launch by spallation: implications for lithopanspermia. Astrobiology 9:647–657
Head JN, Melosh HJ, Ivanov BA (2002) Martian meteorite launch: high-speed ejecta from small craters. Science 298:1752–1756
Horneck G, Stöffler D, Ott S, Hornemann U, Cockell CS, Moeller R, Meyer C, de Vera J-P, Fritz J, Schade S, Artemieva NA (2008) Microbial rock inhabitants survive impact and ejection from host planet: first phase of lithopanspermia experimentally tested. Astrobiology 8:17–44
Melosh HJ (1984) Impact ejection, spallation, and the origin of meteorites. Icarus 59:234–260
Melosh HJ (1985) Ejection of rock fragments from planetary bodies. Geology 13:144–148
Melosh HJ (1988) The rocky road to panspermia. Nature 332:687–688
Melosh HJ (2003) Exchange of meteorites (and life?) between stellar systems. Astrobiology 3:207–215
Mileikowsky C, Cucinotta F, Wilson JW, Gladman B, Horneck G, Lindegren L, Melosh J, Rickman H, Valtonen M, Zheng JQ (2000) Natural transfer of viable microbes in space, Part 1: from Mars to Earth and Earth to Mars. Icarus 145:391–427
Stöffler D, Horneck G, Ott S, Hornemann U, Cockell CS, Moeller R, Meyer C, de Vera J-P, Fritz J, Artemieva NA (2007) Experimental evidence for the potential impact ejection of viable microorganisms from Mars and Mars-like planets. Icarus 186:585–588
Valtonen M, Nurmi P, Zheng J-Q, Cucinotta FA, Wilson JW, Horneck G, Lindegren L, Melosh J, Rickman H, Mileikowsky C (2009) Natural transfer of viable microbes in space from planets in the extra-solar systems to a planet in our solar system and vice-versa. Astrophys J 690:210–215
Weiss BP, Kirschvink JL, Baudenbacher FJ, Vali H, Peters NT, Macdonald FA, Wikswo JP (2000) A low temperature transfer of ALH84001 from Mars to Earth. Science 290:791–795
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Melosh, H.J. (2014). Spallation Zone. In: Amils, R., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-27833-4_1477-2
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DOI: https://doi.org/10.1007/978-3-642-27833-4_1477-2
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Publisher Name: Springer, Berlin, Heidelberg
Online ISBN: 978-3-642-27833-4
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