Unfortunately for us, earth has experienced at least five mass extinctions during the past 540 million years. Some scientists believe it may be as many as twenty. In other words, mass extinction events are not uncommon.
As residents of Earth, we've grown accustomed to having just one moon. Let Saturn and its 62 moons be the solar system's showboat; that just leaves us on this planet to enjoy our single natural satellite all the more. Or so we thought.