Ejecta–megaregolith accumulation on planetesimals and large asteroids

摘要: – Megaregolith accumulation can have important thermal consequences for bodies that lose heat by conduction, as vacuous porosity of the kind observed in lunar megaregolith lowers conductivity a factor 10. I modeled global average ejecta function largest impact size, with no explicit modeling time. In conjunction an assumed cratering size-distribution exponent b, crater constrains sizes all other craters significantly contribute to megaregolith. The impactor mass ratio is major fraction catastrophic-disruption ratio, and general crater’s diameter close target’s diameter. Total roughly 1–5% (and proportional to) radius. Global accumulations estimated this approach are higher than classic Housen et al. (1979) study This revision caused mainly (typical) size. For b ∼ 2, single typically contributes 50% total new (nonrecycled) ejecta. Megaregolith be destroyed sintering, process whose pressure sensitivity makes it effective at lower temperature on larger bodies. Planetesimals ∼100 km may surprisingly well suited (about two three times diameter) attaining temperatures conducive widespread melting. A water-rich composition significant disadvantage terms planetesimal heating, shallow interior densified aqueous metamorphism, will low sintering temperature.