Deviations From Natural Abundance
It is now known from study of the sun and primitive meteorites that the solar system was initially almost homogeneous in isotopic composition. Deviations from the (evolving) galactic average, locally-sampled around the time that the sun's nuclear burning began, can generally be accounted for by mass fractionation (see the article on mass-independent fractionation) plus a limited number of nuclear decay and transmutation processes. There is also evidence for injection of short-lived (now extinct) isotopes from a nearby supernova explosion that may have triggered solar nebula collapse. Hence deviations from natural abundance on earth are often measured in parts per thousand (per mil or ‰) because they are less than one percent (%).
The single exception to this lies with the presolar grains found in primitive meteorites. These bypassed the homogenization, and often carry the nuclear signature of specific nucleosynthesis processes in which their elements were made. In these materials, deviations from "natural abundance" are sometimes measured in factors of 100.
Read more about this topic: Natural Abundance
Famous quotes containing the words natural and/or abundance:
“Surely knowledge of the natural world, knowledge of the human condition, knowledge of the nature and dynamics of society, knowledge of the past so that one may use it in experiencing the present and aspiring to the future—all of these, it would seem reasonable to suppose, are essential to an educated man. To these must be added another—knowledge of the products of our artistic heritage that mark the history of our esthetic wonder and delight.”
—Jerome S. Bruner (20th century)
“Take care! Be on your guard against all kinds of greed; for one’s life does not consist in the abundance of possessions.”
—Bible: New Testament, Luke 12:15.