What is an enstatite chondrite?
An enstatite chondrite is a chondrite made mostly of iron-free enstatite pyroxene, formed in very oxygen-poor conditions, with isotopes similar to Earth's.
Enstatite chondrites are a class of chondrites named after their main mineral, enstatite, a magnesium pyroxene containing almost no iron. They make up about 1 to 2 per cent of meteorite falls.
Formed with little oxygen. Enstatite chondrites formed in extremely reducing conditions. Most of their iron is in metal and sulfides rather than in silicates. Their metal contains dissolved silicon, and they contain unusual minerals such as oldhamite, a calcium sulfide, and niningerite or alabandite, magnesium and manganese sulfides. Such minerals are almost never found in Earth rocks.
Two groups. EH chondrites have high total iron and small chondrules. EL chondrites have lower iron. Each probably comes from a separate parent body. Many ELs are petrologic type 6, while many EHs are types 3 to 5.
Examples. Abee, an EH4 that fell in Canada in 1952; Indarch, an EH4 that fell in Azerbaijan in 1891; and Hvittis, an EL6 that fell in Finland in 1901.
Link to Earth. Enstatite chondrites have oxygen isotopes, and isotopes of several other elements, almost identical to those of Earth and the Moon. This has led some scientists to suggest that much of Earth was built from enstatite-chondrite-like material. A 2020 study found enough hydrogen in them to have supplied a significant amount of Earth's water. However, their chemistry does not match Earth exactly.
Care. Their sulfides react with moisture, so they need dry storage.
Aubrites, igneous enstatite meteorites, may come from a related, melted parent body.