The early atmosphere of Earth, formed approximately 4.6 billion years ago, was primarily composed of gases released from volcanic activity.
Composition of the Early Atmosphere
Here's a breakdown of the main components:
- Hydrogen Sulfide (H₂S): A toxic gas with a distinct rotten egg smell.
- Methane (CH₄): A simple hydrocarbon and potent greenhouse gas.
- Carbon Dioxide (CO₂): A significant component, with levels ranging from 10 to 200 times higher than what is present in the atmosphere today.
Why these gases?
These gases were primarily the result of volcanic outgassing from the Earth’s mantle.
Comparison to Today's Atmosphere
The early atmosphere is dramatically different from the nitrogen-oxygen-rich atmosphere we have today. Specifically, the high concentration of carbon dioxide is a significant difference compared to current levels.
Table Summary
| Gas | Early Atmosphere Concentration | Present Atmosphere Concentration |
|---|---|---|
| Hydrogen Sulfide | Present | Very Low |
| Methane | Present | Trace Amount |
| Carbon Dioxide | 10-200 times higher than present levels | Relatively low |
| Nitrogen | Likely present, exact quantities uncertain | ~78% |
| Oxygen | Likely negligible/ absent | ~21% |
