Washington, D.C. Life originated as a result of natural processes that exploited early Earth's raw materials. Scientific models of life's origins almost always look to minerals for such essential tasks as the synthesis of life's molecular building blocks or the supply of metabolic energy. But this assumes that the mineral species found on Earth today are much the same as they were during Earth's first 550 million yearsthe Hadean Eonwhen life emerged. A new analysis of Hadean mineralogy challenges that assumption. It is published in American Journal of Science.
Carnegie's Robert Hazen compiled a list of every plausible mineral species on the Hadean Earth and concludes that no more than 420 different mineralsabout 8 percent of the nearly 5,000 species found on Earth todaywould have been present at or near Earth's surface.
"This is a consequence of the limited ways that minerals might have formed prior to 4 billion years ago," Hazen explained. "Most of the 420 minerals of the Hadean Eon formed from magmamolten rock that slowly crystallized at or near Earth's surfaceas well as the alteration of those minerals when exposed to hot water."
By contrast, thousands of mineral species known today are the direct result of growth by living organisms, such as shells and bones, as well as life's chemical byproducts, such as oxygen from photosynthesis. In addition, hundreds of other minerals that incorporate relatively rare elements such as lithium, beryllium, and molybdenum appear to have taken a billion years or more to first appear because it is difficult to concentrate these elements sufficiently to form new minerals. So those slow-forming minerals are also excluded from the time of life's origins.
"Fortunately for most origin-of-life models, the most commonly invoked minerals were present on early Earth," Hazen said.
For example, clay mineralssometimes theorized by chemists to trigger interesting reactionswere certainl
|Contact: Robert Hazen|