Is it ensure, insure, or assure?
a diverse class of chondrites (one of the two divisions of stony meteorites), important because of the insights they provide into the early history of the solar system. They comprise about 3 percent of all meteorites collected after being seen to fall to Earth. Carbonaceous chondrites are subdivided into six well-established groups-CI, CM, CV, CO, CR, and CK-based on their bulk chemistry, petrology, and oxygen isotopic compositions. Two additional groups, named CH and CB, has also been tentatively identified. Like all chondrites, carbonaceous chondrites (with the exception of the CI group) are composed principally of chondrules and refractory inclusions set in a fine-grained matrix