How to make a habitable planet

Abstract

The dust clouds orbiting second (and later) generation stars eventually collect into planets. It appears, based on our own solar system, that planets near the central star will be rocky, while those farther away will become gas giants. The compositions of meteorites show that volatile compounds of carbon, nitrogen, oxygen and hydrogen should be abundant in rocky planets, and could be released during and after accretion of the planets themselves to give primitive atmospheres and oceans. The earliest atmospheres would have contained abundant reduced gases such as methane (CH₄) and ammonia (NH₃) as well as water vapor, nitrogen and perhaps hydrogen sulfide (H₂S).