Mineral Makeup of Earth Has Changed Drastically Over Time, Study Suggests

Earth's mineral species were far different 550 million years ago when life first took root than they are today, a new analysis published in the American Journal of Science posits.

The vast majority of those models used to divine the origin of life rely on the assumption that those mineral species we see now are essentially equivalent to those found throughout Earth's history, including the Hadean Eon, which is attributed with the origins of life. 

According to Robert Hazen of the Carnegie Institution for Science, this is far from the case.

Hazen compiled a list of every plausible mineral species on the Hadean Earth, concluding that only about 8 percent of the nearly 5,000 species found today would have existed back then.

"This is a consequence of the limited ways that minerals might have formed prior to 4 billion years ago," Hazen said in a 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 modern mineral species are the result of life: shells, bones, and life's chemical byproducts such as as oxygen from photosynthesis have given way to thousands of new mineral species.

What's more, many others that incorporate relatively rare elements appear to have taken 1 billion years -- if not more -- to become concentrated enough to form new minerals.

"Fortunately for most origin-of-life models, the most commonly invoked minerals were present on early Earth," Hazen said.

Clay, believed by some to have triggered key reactions, and sulfide minerals, such as iron and nickel, were all present back then. Others, such as borate and molybdate, were probably not, which poses an issue for those origin models that rely on them.

One quesiton that remain unanswered regarding the Hadean Eon is that surrounding the higher rate of impact by asteroids and comets during experienced back then, which would have created extensive fracture zones filled with hot circulating water. These areas, Hazen notes, could have created diverse zones with a wide range of unique minerals. 

The study's implications reach beyond our own planet, Hazen says, suggesting that the Mars we see today may have progressed only as far as the Earth's Hadean Eon. If he's right, the Red Planet is only be home to some 400 different mineral species -- a fact NASA continues to explore through the help of its rovers.