Life appeared on Earth as early as the Archaic Era, more than 3.6 billion years ago, in oceans with a composition very different from the one we know today. A new study also reveals the extent to which geological processes may have affected the concentration of certain metals, nutrients essential for metabolic reactions.
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If we know that life arose in the oceans, few constraints currently exist on the chemical composition of these primitive oceans, and in particular on the presence of nutrientsnutrients because they were able to promote the emergence of the first organisms.
If today the zinczinc and the buyerbuyer are among the nutrients essential for all life on Earth, especially for the formation of proteinproteinResearch shows that the very first life forms may have preferred others metalmetal. THE ironironTHE molybdenummolybdenum and the manganesemanganese were in fact visibly preferentially selected to form the proteins of the first metabolic organisms. A deviation from the current situation that could indicate that these metals were present in significant concentrations in the Archean oceans 3.6 billion years ago. But how can we explain this difference in the composition of the oceans compared to today? Two researchers may have found the answer: the presence of a certain mineral, groenalite.
A primitive mini-ocean in the laboratory
To understand this, we must remember that at that time no photosynthetic organisms had yet appeared and that the atmosphere, like the oceans, was very oxygen-poor. Analysis of rare sedimentary rocks from theArcheanArchean also shows that the waters of the globe were rich in iron and silicasilica. But for the rest, and especially regarding the concentrations of different nutrients, the question remains open.
To try to find out the exact composition of Archean seawater, scientists decided to recreate a miniature ocean in the laboratory, based on data taken from Archean sedimentary rocks to constrain the environmental conditions of the oceanic environment.
Appearance of a new mineral and impact on metal concentrations
The researchers soon observed the formation of a new mineral: it was a silicatesilicate ferruginous, called greenalite. An observation supported by the analysis of Archean rocks showing that greenalite was certainly an important mineral on the SoilSoil primitive, maybe even one of the mineralsminerals the most important of the Archaic.
But while greenalite is formed by the reaction of silica and iron in water, scientists are observing another phenomenon: a drastic change in the concentrations of certain metals. Zinc, copper and vanadiumvanadium are in fact absorbed by the greenalite. Seawater is therefore depleted of these nutrients and relatively enriched in manganese, molybdenum and cadmiumcadmium, unaffected by the formation of the new mineral. These results, published in the journal Natural Geosciencestherefore agree with biologists’ predictions about the preference of early metabolic systems to utilize these nutrients, which are available in large quantities.
Experience also shows that greenalite can form in a deep environment at the level of hydrothermal springshydrothermal springs, just like in shallow water. The formation of this mineral would also have had a lasting impact on the composition of the oceans by permanently storing zinc, copper and vanadium.