Melt pocket
A melt pocket is a small patch of glass or fine crystals formed by local melting during a shock event.
A melt pocket is an isolated patch, typically millimetres across, where a meteorite melted during an impact and then quenched to glass or fine crystals. Unlike shock veins, which form thin networks, melt pockets are rounded or irregular blobs.
They form because a shock wave does not compress rock evenly. Pores, cracks and boundaries between hard and soft minerals focus energy, heating small regions far above the average temperature. In Martian shergottites, melt pockets are common and have trapped bubbles of gas whose composition matches the Martian atmosphere measured by the Viking landers, a key line of evidence for their origin.
Melt pockets often contain high-pressure minerals and vesicles, and they can reset some radiometric clocks locally. Their study helps scientists judge the peak pressure and temperature of the impact that affected a meteorite, which in Martian rocks is the event that ejected them from Mars.
Related terms
Level: Expert Advanced