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拍品专文
Vesta is the second largest asteroid and the only large one covered with basalt -- the same fine-grained volcanic rock that spews from Hawaiian volcanoes, makes up the dark areas of the Moon and the huge shield volcanoes on Mars. Three groups of achondrites (igneous meteorites) are widely thought to have come from Vesta; these are the HED meteorites – Howardites, Eucrites and Diogenites. Eucrites are basalts derived from the surface and upper crust of Vesta; diogenites are from the deep crust; and howardites are impact mixtures of both groups. Diogenites are rare objects, making up just 0.7% of known meteorites. NWA 4664 is the 4664th sample to be catalogued following its recovery in the Northwest African grid of the Sahara Desert.
The meteorite was part of a huge asteroid fragment excavated from the lower crust of Vesta by an enormously energetic collision early in Solar-System history. Over the ensuing eons, pieces broke off this fragment. This meteorite probably broke off a few million years ago and was sent on a collision course with Earth.
The cut face of the meteorite has a fine-grained texture, the result of impact pulverization. Sprinkled in are coarser grains that cooled slowly at depth within Vesta and managed to avoid substantial crushing.
The meteorite was part of a huge asteroid fragment excavated from the lower crust of Vesta by an enormously energetic collision early in Solar-System history. Over the ensuing eons, pieces broke off this fragment. This meteorite probably broke off a few million years ago and was sent on a collision course with Earth.
The cut face of the meteorite has a fine-grained texture, the result of impact pulverization. Sprinkled in are coarser grains that cooled slowly at depth within Vesta and managed to avoid substantial crushing.