| 1 | These scientists pay close attention to the changes in the atmosphere. | |
| 2 | This planet, we think, is likely to have a fairly substantial atmosphere. | |
| 3 | The Earth is made up of three concentric zones: the lithosphere (solid earth), the hydrosphere(water layer), and the atmosphere. | |
| 4 | The early Proterozoic atmosphere and hydrosphere are similar to those of Archaeozoic in being still absent in oxygen. | |
| 5 | Solar energy enters the earth atmosphere as light, and it is radiated by the earth surface as heat. |