Impact crater formed in highly porous material by compaction and pore-space collapse instead of excavation.
Impact crater formed by pore-space collapse or compaction that results in a little or no ejecta blanket beyond the crater rims. On the other hand, not all craters lacking ejecta blankets are compaction craters. The lack of ejecta may also be due to low gravity and/or difficulty of being recognized (e.g., little color/morphological contrast). A notable example of a regular crater lacking evident ejecta blanketing is represented by the 50-km crater Massilia observed on asteroid Lutetia (Marchi et al. 2011).
Proposed Mechanisms to Explain Target Material Porosity
The shrinking (e.g., porosity collapse – gravitational self-compaction) and differentiation of a sufficiently large body result in converting potential gravitational energy into heat. Internal warming...
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