From “Setting the Stage for Life: Scientists Make Key Discovery About the Atmosphere of Early Earth” (ScienceDaily, Nov. 30, 2011), we learn:
Scientists in the New York Center for Astrobiology at Rensselaer Polytechnic Institute have used the oldest minerals on Earth to reconstruct the atmospheric conditions present on Earth very soon after its birth.
For decades, scientists believed that the atmosphere of early Earth was highly reduced, meaning that oxygen was greatly limited. Such oxygen-poor conditions would have resulted in an atmosphere filled with noxious methane, carbon monoxide, hydrogen sulfide, and ammonia. To date, there remain widely held theories and studies of how life on Earth may have been built out of this deadly atmosphere cocktail.
Now, scientists at Rensselaer are turning these atmospheric assumptions on their heads with findings that prove the conditions on early Earth were simply not conducive to the formation of this type of atmosphere, but rather to an atmosphere dominated by the more oxygen-rich compounds found within our current atmosphere — including water, carbon dioxide, and sulfur dioxide.
Despite being the atmosphere that life currently breathes, lives, and thrives on, our current oxidized atmosphere is not currently understood to be a great starting point for life. Methane and its oxygen-poor counterparts have much more biologic potential to jump from inorganic compounds to life-supporting amino acids and DNA. As such, Watson thinks the discovery of his group may reinvigorate theories that perhaps those building blocks for life were not created on Earth, but delivered from elsewhere in the galaxy.
The researchers relied heavily on the study of zircons.
We wouldn’t recommend setting the results in stone just yet.