The Earth's continental crust is made up of more than 90 percent of silica-rich minerals such as feldspar and quartz. But where did these silicon-rich minerals come from? And how can knowledge of their origin help in the search for life on other planets?
The most popular theory is that all the components of the early Earth's crust were formed by volcanic activity. However, today geophysicists from McGill University, Canada, Don Baker and Kassandra Sofonio published a paper calling for a new angle of this crustal formation. According to this work, some of the chemical constituents of this material were deposited on the surface of the early Earth from the vapor atmosphere that existed at that time.
Almost indisputable today for geophysicists is the hypothesis that about 4.5 billion years ago, a planetoid the size of Mars crashed into the surface of our planet, which led to the melting of Earth's material and turning it into an ocean of magma. After this collision - from the fragments of which, by the way, the Moon could have formed - the Earth's surface gradually solidified until it became solid. Baker does not reject the hypothesis of such a collision either.
However, according to Baker, the Earth's atmosphere after the collision, consisting of superheated steam under high pressure, dissolved rocks in itself, which then fell to the surface in the form of solid drops with the so-called "silicate rains."
To test their hypothesis, Baker and Sofonio conducted laboratory experiments on the dissolution of silicates previously melted in the presence of water at 1550 degrees Celsius and ground into powder in gold-palladium capsules at a temperature of 727 degrees Celsius and a pressure of about 100 atmospheres - conditions corresponding to the conditions that existed on the surface of our planet about 1 million years after the collision that formed the moon. The authors of the work noted a surprisingly close similarity between the model silicates dissolved in a steam atmosphere in a laboratory experiment and the rocks found in the composition of the earth's crust.
“Our experiments reveal the chemistry of this process,” says Baker. "In addition, they will help scientists develop new criteria for the search for potentially habitable exoplanets."
The study was published in the journal Earth and Planetary Science Letters.