Since many current life-origin models rely on minerals available on Earth, a new analysis of Hadean mineralogy challenges the assumption that minerals found today are the same as they were during the Hadean Eon.
According to many studies, life on earth evolved through natural processes that exploited the Earth's raw minerals. Life origin models rely on minerals to help rebuild how life's molecular building blocks or metabolic energy formed. However, this is based on the assumption that minerals found today are the same as they were during the Hadean Eon -550 million years ago, when life first emerged.
A new analysis of Hadean mineralogy challenges this assumption. Carnegie Institution's Robert Hazen first compiled a list of all mineral species on Earth during the Hadean Eon and found that no more than 420 different minerals existed at or near the Earth's surface during that time compared to the 5,000 species found on the planet today.
"This is a consequence of the limited ways that minerals might have formed prior to 4 billion years ago," Hazen explained in a press statement. "Most of the 420 minerals of the Hadean Eon formed from magma-molten rock that slowly crystallized at or near Earth's surface-as well as the alteration of those minerals when exposed to hot water."
Many of the minerals found today have resulted from the growth of living organisms like bones and shells. Some of these are also life's chemical byproducts like oxygen produced during photosynthesis. Hundreds of new elements available today are an amalgamation of lithium, beryllium, and molybdenum, which appeared for the first time on Earth billions of years after life first emerged. This is because it is not easy to get the perfect combination of lithium, beryllium, and molybdenum to form a new mineral. Therefore, these slow-forming new minerals also need to be excluded from models based on life's origin.
"Fortunately for most origin-of-life models, the most commonly invoked minerals were present on early Earth," Hazen said.
Researchers confirmed that clay minerals and sulfide minerals including varieties of nickel and iron were widely available during life's origin to catalyze organic reactions. However, it is very unlikely that minerals rare even today, like borate and molybdate minerals were available on Earth during the Hadean Eon. This fact then raises questions about life-origin models based on these minerals.
Even today, there are still many unanswered questions about the paleomineralogy of the Hadean Eon, leaving scope for more studies on the topic. One vast difference between the Hadean Eon and today is the frequency of impacts of large asteroids and comets. These impacts may have caused massive destructions of the Earth's crust and the creation of large fracture zones that were later filled with hot circulating water. These hydrothermal areas may have created complex zones with many exotic minerals.
Also unanswered are questions pertaining to how other planets and moons evolved minerlogically. According to Hazen, Mar's "mineralogic" evolution may have gone as far as the Earth's did till the Hadean Eon, suggesting it may have only about 400 minerals. Thanks to advancements and discoveries by Mar's Curiosity Rover, this speculation may soon be confirmed.
