You may omit the comma following a short introductory phrase: On Thursday the committee decided the dispute. In 1954 the Supreme Court desegregated the public schools. But if you omit this comma once, you should do the same throughout the paper for all short introductory phrases.
But, over time the differences seen among the ever growing number of these visitors has led to many more categories than three. At the present there are approximately fifty types of meteorites recognized. They still fall mainly into the three original families; the irons, the stony-irons and the stones.
Ordinary chondrites are by far the most common type of meteorite to fall to Earth: about 80% of all meteorites and over 90% of chondrites are ordinary chondrites. 1  They contain abundant chondrules, sparse matrix (10â15% of the rock), few refractory inclusions, and variable amounts of Fe-Ni metal and troilite (FeS).