A petrographic assessment, using features observed in minerals grains, of the degree to which a Work in progress. A solid natural object reaching a planet’s surface from interplanetary space. Solid portion of a meteoroid that survives its fall to Earth, or some other body. Meteorites are classified as stony meteorites, iron meteorites, and stony-iron meteorites. These groups are further divided according to their mineralogy and Click on Term to Read More has undergone shock metamorphism. The highest stage observed in 25% of the indicator grains is used to determine the stage. Also called “shock level”.
|Shock Stage||Description||Pressure (GPa)||Temperature Increase (K)||Features|
|S1||Unshocked||< 5||10||Sharp optical In astronomy, the dimming of starlight as it passes through the interstellar medium. Dust scatters some of the light, causing the total intensity of the light to diminish. It is important to take this effect into account when measuring the apparent brightness of stars. The dark bands running across portions Click on Term to Read More viewed in microscope
Small number of irregular fractures
|S2||Very Weakly Shocked||5 - 10||20||Undulatory extinction
|S3||Weakly Shocked||10 - 20||100||Group of silicate minerals, (Mg,Fe)2SiO4, with the compositional endpoints of forsterite (Mg2SiO4) and fayalite (Fe2SiO4). Olivine is commonly found in all chondrites within both the matrix and chondrules, achondrites including most primitive achondrites and some evolved achondrites, in pallasites as large yellow-green crystals (brown when terrestrialized), in the silicate portion Click on Term to Read More: fractures
Also referred to as the plagioclase feldspar series. Plagioclase is a common rock-forming series of feldspar minerals containing a continuous solid solution of calcium and sodium: (Na1-x,Cax)(Alx+1,Si1-x)Si2O8 where x = 0 to 1. The Ca-rich end-member is called anorthite (pure anorthite has formula: CaAl2Si2O8) and the Na-rich end-member is albite Click on Term to Read More: undulatory extinction
|S4||Moderately Shocked||30 - 35||300||Olivine: weak mosaicism, planar fractures
Plagioclase: undulatory extinction, Same in all directions. in places, planar deformation features.
|S5||Strongly Shocked||45 - 55||600||Olivine: strong mosaicism, planar fractures and planar deformation features
Plagioclase: Natural glass composed of isotropic plagioclase produced during shock metamorphism (not melting) at pressures of ~30 GPa. Maskelynite is commonly found in shergottites though also found in some ordinary chondrites, HED and lunar meteorites. It is also found in association with meteorite impact craters and crater ejecta. Named after British Click on Term to Read More
|S6||Very Strongly Shocked||75 - 90||1500||Olivine: solid state recrystallization and staining, presence of High-pressure olivine polymorph with a spinel structure that is found in highly shocked meteorites (above ~50 GPa, shock level > S5) and the Earth's transition zone mantle (~13 GPa). Under even higher pressure in the lower mantle (~24 GPa), ringwoodite decomposes into perovskite (Mg,Fe)SiO3, and magnesiowüstite (Mg,Fe)O, whose properties are Click on Term to Read More, local melting
Plagioclase: shock melted