The atmosphere during the Archean and Proterozoic eons
The composition of the atmosphere of early Earth remains primarily unknown. While today's atmosphere can be easily described as 78% nitrogen and 21% oxygen, the same is not true for the early history of Earth. It is known that during the Archean eon (~4-2.5 billion years ago), there was likely little to no free oxygen present in the atmosphere because of the reactive nature of free oxygen. It is also known that the surface of Earth was warmer than what can be explained by radiation from the young sun. This discovery supports the idea of carbon dioxide and methane (greenhouse gases) being present in large amounts in the Archean atmosphere. As a result, the atmosphere of early Earth may have resembled that of Titan (a moon of Saturn) whose atmosphere is known to contain oxygen in the form of carbon monoxide, carbon dioxide, and water.
Very similar to Titan today, the high amounts of methane in the atmosphere may have resulted in the formation of photochemical hazes. These hazes on early Earth may have changed the climate in a way that made Earth more habitable. Secondly, these hazes may have been the source of prebiotic molecules. It is known that life on Earth began under these conditions in the form of anaerobic microbes and blue-green algae. These microbes began to break down carbon dioxide in the atmosphere through photosynthesis, releasing free oxygen into the atmosphere as a byproduct.
This release of free oxygen into the atmosphere had many critical ramifications. First, the exposed iron rich rocks absorbed the oxygen which was converted to iron oxide (rust). These "Banded Iron Formations" are used to mark the difference between the Archean and Proterozoic eons around 2.5 billion years ago (when oxygen became the dominant atmospheric species). However, these rocks could not absorb all of the free oxygen being produced and eventually it began to build up in the atmosphere. This build-up of oxygen caused the deaths of much life on Earth since oxygen was poison to those organisms. The excess oxygen also resulted in the destruction of methane in the atmosphere which would have stopped the prebiotic chemistry that was occurring in the hazes of the Archean atmosphere. Lastly, the large removal of greenhouse gases would have resulted in an extreme drop in Earth's temperature which may have caused the first of many snowball Earths.
This aspect of the project will explore the prebiotic chemistry of the hazes of the Archean atmosphere to understand how the addition of free oxygen would affect the photochemical products before destroying the haze. In particular, this part of the project will attempt to detect photochemically produced biomolecules (amino acids, nucleobases) and which conditions are necessary to make them. This portion of the project will be done while working in close association with Dr. Shawn Domagal-Goldman, a planetary modeler at NASA GSFC.
Very similar to Titan today, the high amounts of methane in the atmosphere may have resulted in the formation of photochemical hazes. These hazes on early Earth may have changed the climate in a way that made Earth more habitable. Secondly, these hazes may have been the source of prebiotic molecules. It is known that life on Earth began under these conditions in the form of anaerobic microbes and blue-green algae. These microbes began to break down carbon dioxide in the atmosphere through photosynthesis, releasing free oxygen into the atmosphere as a byproduct.
This release of free oxygen into the atmosphere had many critical ramifications. First, the exposed iron rich rocks absorbed the oxygen which was converted to iron oxide (rust). These "Banded Iron Formations" are used to mark the difference between the Archean and Proterozoic eons around 2.5 billion years ago (when oxygen became the dominant atmospheric species). However, these rocks could not absorb all of the free oxygen being produced and eventually it began to build up in the atmosphere. This build-up of oxygen caused the deaths of much life on Earth since oxygen was poison to those organisms. The excess oxygen also resulted in the destruction of methane in the atmosphere which would have stopped the prebiotic chemistry that was occurring in the hazes of the Archean atmosphere. Lastly, the large removal of greenhouse gases would have resulted in an extreme drop in Earth's temperature which may have caused the first of many snowball Earths.
This aspect of the project will explore the prebiotic chemistry of the hazes of the Archean atmosphere to understand how the addition of free oxygen would affect the photochemical products before destroying the haze. In particular, this part of the project will attempt to detect photochemically produced biomolecules (amino acids, nucleobases) and which conditions are necessary to make them. This portion of the project will be done while working in close association with Dr. Shawn Domagal-Goldman, a planetary modeler at NASA GSFC.