Carbon dioxide is inexplicably a mere trace gas when it should be the bulk of the air, as it is on other planets.
令人费解的是，二氧化碳理应像在其他行星那样成为大气的主要成分，却仅仅是一种示踪气体。
2
Most models of planets assume that they are similar to the terrestrial planets in our own Solar System, with about half as much carbon as oxygen in the atmosphere.
而多数行星模型均假设它们和我们太阳系的类地行星相似，即在大气中碳含量是氧含量的一半左右。
3
Some commenters felt that Traub's 'habitable zones' were too generous, it included planets shrouded in icy clouds of carbon dioxide.