Matt Simon, writing for Wired:
Here’s what Dick figured. At the time, there were an average of 280 people per square mile in England. And because he thought every surface of our universe bears life, it would naturally occur at roughly the same population density. So from comets and asteroids to the rings of Saturn, if you knew how big something was, you could guess how many beings live there. Thus, Jupiter would be the most populated object in the solar system, with 7 trillion beings. The least populated would be Vesta, the second largest asteroid in the asteroid belt, tallying just 64 million.