“Yes. There is a super-dense class, still smaller, poorer in hydrogen, than the inner planets of the solar system. The ratio of occurrence of hydrogen-ammonia planets and these super-dense water-oxygen worlds of theirs over the entire Galaxy⁠—and remember that they have actually conducted a survey of significant sample volumes of the Galaxy which we, without interstellar travel, cannot do⁠—is about three to one. This leaves them seven million super-dense worlds for exploration and colonization.”

The Industrialist looked at the blue sky and the green-covered trees among which they were making their way. He said, “And worlds like ours?”

The Astronomer said, softly, “Ours is the first solar system they have found which contains them. Apparently the development of our solar system was unique and did not follow the ordinary rules.”

The Industrialist considered that. “What it amounts to is that these creatures from space are asteroid-dwellers.”