Birth of gold and silver - how the precious metals were created
Neutron Star Collision Becomes the Birth Agent
The formation of new elements requires extremely high temperatures. For example, in the interior of the sun, the fusion of hydrogen into helium produces temperatures of 10 mill. degrees. However, much higher temperatures are required to form heavier elements. For a long time it was thought that a supernova, i.e. the explosion of a star at the end of its lifetime, could cause sufficiently high temperatures to be able to form precious metals. However, it has been shown that while a large number of elements are formed, almost no precious metals are formed; according to model simulations, this is only the case when two neutron stars collide and merge. Neutron stars, which themselves arise from supernova explosions and have an extremely high density, orbit each other at high speed, spiraling towards each other until they finally merge and collapse into a black hole.
In this process, high-energy flashes (gamma rays) or cosmic explosions are created, which are only surpassed by the Big Bang and release more energy in one second than our sun in the course of its entire existence. Temperatures of up to one trillion degrees occur, the highest ever in the universe, hundreds of thousands of times higher than in the interior of the sun. According to complex computer-aided calculations, this leads to the formation of heavy elements such as silver. It can thus also be understood why these metals are among the few that also occur in elemental form in the earth's crust. Neutron star mergers occur in our galaxy only every few million years. Given that there are more than 100 billion stars in the Milky Way, more than half of which are in binary or multiple star systems, this is surprisingly rare. Assuming that it takes place in the Milky Way and all other galaxies of the universe on average every 10 mill. years, such an inferno would occur somewhere in the universe about once per hour with about 100 billion galaxies. Enormous pressure waves are generated, whereby matter is hurled far into interstellar space.
Earth core "swallows" precious metals of the proto-earth
In the early stages of the solar system's formation process, dust particles began to clump together and form trillions of planetesimals. Due to their gravitational pull, these fused together and gained mass. As they grew in size, they then absorbed smaller planetesimals. As a result, protoplanets were formed, including proto-Earth. Initially, the temperatures on the proto-Earth were very high, so that its surface was in a gaseous or liquid state. Since heavy elements such as precious metals tend to combine with iron in a molten state, they were drawn into the iron- and nickel-containing core of the still young planet. In this respect, there should not actually be any precious metals in the Earth's crust. How is it to be explained therefore that these occur there nevertheless? Also to this computer simulations gave a hint: The relative frequency of the formation of heavy elements accompanying with a neutron star fusion agrees to a large extent with that in the earth's crust as well as with that, which was found in metallic meteorites fallen on the earth. The formation of heavy elements in the earth's crust is a very important factor for the formation of precious metals
Precious metals of the Earth's crust are of extraterrestrial origin
The Proto-Earth initially had a much smaller mass than the Earth today. At that time, however, comparatively much interplanetary matter still vagabonded through the solar system, so that the Proto-Earth was inevitably confronted with it. Its mass increased thus by impacts of smaller celestial bodies, at first the still numerous remaining planetesimals, later then comets, asteroids and meteorites. When these got into the gravitational field of the proto-Earth, it added them to its not yet solidified body, which had not yet formed an atmosphere, so that the celestial bodies could impact relatively unhindered. In this early phase of the Earth's history there was a drastic event: 30 mill. years after its formation it collided with a celestial body which had 10-15 % of its mass. It is easy to imagine what a devastating effect a frontal instead of lateral collision with the planetesimal in size of Mars could have had.
As a result of the collision, matter from the proto-Earth and planetesimal was hurled into space and captured in Earth orbit, forming the protomoon, which can be deduced from a comparison of the isotopes in the Earth and moon rocks. The celestial body that collided with the proto-Earth is named Theia after Titan, who gave birth to Selene, the goddess of the moon. What seems to be a devastating visitation at first sight, was of central importance in earth-historical in several respects: Theia had formed at the same distance from the sun as the proto-earth, but since the planetesimal was much smaller than the proto-earth, the proximity to the sun had a fundamentally different effect on it. For example, it contained those volatile elements such as hydrogen, oxygen, and nitrogen that the proto-Earth had radiated into space due to its initially very high temperatures and lack of an atmosphere.
The elements that had previously volatilized were now added back to the proto-Earth by Theia. This was the prerequisite for the formation of an atmosphere as well as water and thus life on Earth. A further effect caused by Theia should become of crucial importance for the further development of the earth: The protomoon orbited the protoearth initially only in a distance of 60 thousand kilometers, whereby extreme tidal forces acted on the protoearth, in addition it was deformed ovoid, which led to massive friction forces due to the thereby moved, partly still liquid rock masses. The rotation speed of the protoearth was slowed down by this and the protomoon moved away. This had again the consequence that the forces reduced, which worked on a compression of the earth body and an attraction of heavy elements into the earth core. Without Theia the earth would have today probably a density which would be so high that a soil cultivation would not be to be thought, certainly not a precious metal extraction. Thus a cosmic catastrophe of apocalyptic extent proved once again as a stroke of luck for the today's living conditions of our planet.
Earth-historical processes run in extremely long periods. It took thus approximately two billion years, until the surface temperature on earth cooled down from 2000 to under 100 degrees, the earth's crust had solidified to a large extent and a stable atmosphere had developed. The gradual decrease of the impact of celestial bodies on the earth was thereby co-decisive for the occurring cooling of the surface temperature and the increasing solidification of the surface. In this period the earth's crust or the upper layer of the earth's mantle must have bound precious metals and other heavy metals, which supplied it the heavenly bodies hitting it as precious metal reservoirs. This probably came to a conclusion three billion years ago, when the interplanetary matter vagabonding in the solar system thinned out and a more stable atmosphere formed, so that the remaining celestial bodies could no longer strike the Earth unimpeded.
According to a differing theory, there may have been a supernova explosion after the formation of the protoplanets that caused the planets to be bombarded with precious metals.Aside from the fact that supernovae are not capable of forming precious metals on the scale that they occur on Earth, this theory is seemingly impossible to dismiss for two reasons: First, it would be a good explanation for the fact that precious metals are relatively evenly distributed in the Earth's crust and are found in trace amounts in every rock or clump of rock worldwide; second, the primordial cloud would not have had to bind the precious metals. A planet could catch metals easily because of its resistance, while a matter cloud would rather pass heavy metals to continue their way in the interstellar space. Nevertheless, the theory is to be doubted, because it would have come then probably to no planet formation, since for this the necessary elements would have been missing. Also the formation of the sun required an energy shock, without which the matter cloud would not have been set into rotation and the necessary gravitational force would not have arisen, unless a supernova would have triggered this, supplemented by a later neutron star collision. However, the coincidence of two such events in a comparatively short time in a relatively small space seems rather unlikely.
Since the formation of the Earth, almost 500 more neutron star collisions have occurred in the Milky Way. For example, 439 million years ago, high-energy gamma rays from such an inferno hit the Earth, obliterating the ozone layer, leaving animals and plants unprotected from the sun's ultraviolet radiation and causing 95% of species to die out. 200 million years later, the dinosaurs began to appear in the Milky Way. Years later the dinosaurs began to dominate the earth, before 65 mill. years ago also they became extinct by a cosmic disaster, when the impact of a meteorite whirled up so much dust that the sky darkened, the temperatures sank and the dinosaurs were robbed of their food basis. This was, for the time being, the last affliction of the earth, which ultimately paved the way for man to take over the reigns of the planet himself and to mine precious metals, among other things, today.