In 1973, our solar system seemed a quieter place. Sure, the evidence of impacts recorded on the Moon were there for everyone to see, but most of those impacts happened billions of years ago. Astronomers and geologists considered impacts by extraterrestrial bodies to be interesting, but not necessarily a major force still shaping the surfaces of worlds.
Bubbling under the top 10
A lot has happened in astronomy these past 35 years, and it wasn't easy to whittle down our list of the top 10 discoveries. Here are five more breakthroughs that just missed our list.
