Complex sentence: The Allende fall occurred on February 8,1969 over Chihuahua, Mexico and resulted in planetary scientists acquiring a large mass of primitive carbonaceous chondrites as the field was growing and developing instrumentation for the return of moon rocks by the Apollo program.
Split into simpler sentences: The Allende fall occurred on February 8,1969 over Chihuahua, Mexico. The fall resulted in the sudden availability of a large mass of a highly primitive carbonaceous chondrite to planetary scientists just at the time the field was growing and developing instrumentation in anticipation of the return of moon rocks by the Apollo program.