The debate over what makes a planet, well, a planet is nothing new. Pluto wasn't the first object to stir up controversy. In this issue, learn how the discovery of asteroids more than two centuries ago reshaped how we think about our solar system. And in "Running with Rockhounds," learn the basics of meteorite collecting and what spurs meteorite collectors the world over to chase after these rocks from space.
Note: This back issue is available only as a digital download