Complex sentence: The Mazapil meteorite has sometimes been attributed to the comet, but this idea has been out of favor since the 1950s as the processes of differentiation required to produce an iron body are not believed to occur in comets.
Split into simpler sentences: The Mazapil meteorite has sometimes been attributed to the comet, but this idea has been out of favor since the 1950s. The processes of differentiation required to produce an iron body are not believed to occur in comets.