"If there was no water on Earth, what would the Earth atmosphere energy balance be like, and what effect would it have on animal life on Earth?"
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Question
What were the earliest forms of life on earth?
We don't know, because we have almost no surviving rock from earlier than 4.0 billion years ago, at the time life was forming on Earth. Most astrobiologists think that the earliest life forms have not survived to today. They may have been similar to viruses, and there is also evidence suggesting the existence of a "RNA World" before there were life forms that used DNA to reproduce and regulate their chemical processes. By about 3.9 billion years ago there is an indication from the chemistry of the rocks formed then that life might have been extensive in those ancient oceans. The oldest reliably identified fossils date from about 3.4 billion years, and many astrobiologists think these were probably similar to the cyanobacteria that we have today. For an entertaining account of the search for evidence of this ancient life, I recommend the book by J. William Schopf called "Cradle of Life: The Discovery of Earth's Oldest Fossils." David Morrison
NAI Senior Scientist
March 28, 2007
- How frequently are questions answered?
- I asked a question but there was no answer?
- Who is the Astrobiologist answering these questions?
- Will I get an email when my question is answered?
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- How can I get a job as an astrobiologist at NASA?
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- Is it true that the Sun will be in the center of the Milky Way Galaxy in December 2012 and that this will cause a pole shift and massive destruction.
- Has NASA discovered life on other worlds?
- Astrobiology Career Path Suggestions
