Astrophysicists from Lawrence Livermore National Laboratory and Arizona State University reported a new analysis of the oldest meteorite material found on Earth that is not of Earth origin in the Oct. 6, 2013, edition of the journal Proceedings of the National Academy of Sciences.
The researchers examined the composition of the calcium-aluminum-rich inclusions (CAIs) in meteorites and found a consistent composition that indicates the preferential process that formed the earliest solid matter in the universe was the rapid neutron addition process (r-process) that was the result of the action of supernovae.
The high neutron density materials created were reduced to the present abundance of materials with an atomic weight less than 140 by beta decay. This process formed the high nickel, strontium, molybdenum, and barium contents that are present in the majority of meteorite inclusions that have been found on Earth.
The researchers propose that CAIs initially formed in the presence of young suns. No supernova activity occurred until the meteorite material had escaped from the region around the young suns. Subsequent exposure to supernova activity altered the chemical composition of the meteorite materials.
This discovery explains why meteorites differ in chemical composition from the dust and other particulate matter that exists throughout the universe.