²⁶Al in eucrite Piplia Kalan: plausible heat source and formation chronology

Abstract

Aluminum-magnesium isotopic analysis of plagioclase in the eucrite Piplia Kalan, with ²⁷Al/²⁴Mg ratio between 2000 to 7000, reveals the presence of excess magnesium-26 resulting from in situ decay of the short-lived nuclide aluminum-26. This observation confirms aluminum-26 as a plausible heat source for melting and differentiation of the eucrite parent body in particular and for planetesimals in general. The inferred initial abundance of ²⁶Al/²⁷Al of (7.5 ± 0.9) × 10^-7 indicates that melting, differentiation, and crust formation in the parent body of Piplia Kalan was complete within 5 million years of the formation of the solar system.