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.
Stony meteoritesChondrites (85.7%)CarbonaceousEnstatiteAchondrites (7.1%)HED groupSNC groupAubritesUreilites Stony iron meteorites (1.5%)PallasitesMesosideritesIron meteorites (5.7%)Stony-iron meteorites are composed of approximately 50% nickel-iron and 50% silicate material. They make up only 1 to 2% of all meteorites.bout 33% of the meteorites are witnessed falls.A very large number of meteoroids enter the Earth's atmosphere each day amounting to more than a hundred tons of material. But they are almost all very small, just a few milligrams each. Only the largest ones ever reach the surface to become meteorites.