“Then, sir, consider that for a long time our astronomers have believed that two general classes of planetary bodies existed. First, the planets which formed at distances far enough from their stellar nucleus to become cool enough to capture hydrogen. These would be large planets rich in hydrogen, ammonia and methane. We have examples of these in the giant outer planets. The second class would include those planets formed so near the stellar center that the high temperature would make it impossible to capture much hydrogen. These would be smaller planets, comparatively poorer in hydrogen and richer in oxygen. We know that type very well since we live on one. Ours is the only solar system we know in detail, however, and it has been reasonable for us to assume that these were the only two planetary classes.”

“I take it then that there is another.”