Discovery of coesite and stishovite in eucrite

摘要: Howardite–eucrite–diogenite meteorites (HEDs) probably originated from the asteroid 4 Vesta. We investigated one eucrite, Bereba, to clarify a dynamic event that occurred on Vesta using shock-induced high-pressure polymorph. discovered polymorphs of silica, coesite, and stishovite originating quartz and/or cristobalite in around shock-melt veins Bereba. Lamellar formed silica grains through solid-state phase transition. A network-like rupture was melting took place along grains. Nanosized granular coesite crystallized melt. Based polymorphs, estimated shock-pressure condition ranged ∼8 ∼13 GPa. Considering radiometric ages shock features, led formation ca. 4.1 Ga ago, which corresponds late heavy bombardment period (ca. 3.8–4.1 Ga), deduced lunar cataclysm. There are two giant impact basins south pole Although origin HEDs is thought be related events 1.0 our findings at variance with idea.