We are just beginning to discover what Earth’s inner core is really made of
The nucleus rich in iron at Center of our planet was a crucial part of the evolution of the earth. The nucleus feeds not only the magnetic field which protects our atmosphere and the oceans from solar radiation, but it also influences the tectonics of the plates which have continually reshaped the continents.
But despite its importance, many of the most fundamental properties nucleus are unknown. We do not know exactly how hot the nucleus is, of which it is done or when it started to freeze. Fortunately, A recent discovery By me and my colleagues brings us much more to respond to these three mysteries.
We know that the temperature of the inner nucleus of the earth is very 5,000 Kelvin (K) (4,727 ° C). It was once liquid, but has cooled and has become solid over time, developing outwards in the process. As it cools, it releases heat to the suspected coat, causing the currents behind the plates tectonics.
This same cooling also generates the magnetic field of the earth. Most of the energy of the field today comes from the freezing of the liquid part of the nucleus and the growth of the solid inner nucleus in its center.
However, as we cannot access the heart, we must estimate its properties to understand how it is cool.
A key element in understanding the nucleus is to know its melting temperature. We know where the border between the solid internal nucleus and the liquid external nucleus is seismology (the study of earthquakes). The temperature of the nucleus must be equal to its melting temperature in this location, because this is where it is frozen. So, if we know what is the fusion temperature exactly, we can know more about the exact temperature of the nucleus – and what it is done.
Mysterious chemistry
Traditionally, we have two ways to understand what the nucleus is made of: meteorites and seismology. By examining the chemistry of meteorites – which would be pieces of planets that have never been formed, or pieces of destroyed earth planet cores – we can have an idea of what our nucleus could be done.
The problem is that it only gives us approximate idea. Meteorites show us that the nucleus should be made of iron and nickelAnd perhaps a few percent of silicon or sulfur, but it is difficult to be more precise than that.
Seismology, on the other hand, is much more specific. When the sound waves of earthquakes travel through the planet, they accelerate and slow down according to the materials they cross. By comparing the journey time of these waves, from the earthquake to the seismometer, with the speed at which the waves move through minerals and metals in experiences, we can have an idea of what the interior of the earth is done.
It turns out that these journeys require that the heart of the earth be on 10% less dense than pure ironAnd that the liquid outer nucleus is denser than the solid inner nucleus. Only a chemistry known to the nucleus can explain these properties.
But even among a small selection of possible constituents, potential fusion temperatures vary by hundreds of degrees – not leaving us wiser on the precise properties of the nucleus.
A new constraint
In our new research, we used mineral physics to study how the nucleus could first start freezing, discovering a new way of understanding the chemistry of the nucleus. And this approach seems to be even more specific than seismology and meteorites.
Research simulating how the atoms of liquid metals meet to form solids revealed that certain alloys require a more intense “surfer” than others. Supercoling is when a liquid is cooled under its melting temperature. The more intense the surfing, the more the atoms will often meet to form solids, which makes a liquid gel more quickly. A bottle of water in your freezer can be surfed to -5 ° C for hours before gel, while hail is formed in a few minutes when the water droplets are cooled at -30 ° C in the clouds.
By exploring all the possible melting temperatures of the nucleus, we note that the most overflowed the nucleus could have been around 420 ° C below the melting temperature – any more than that and the inner nucleus would be greater than seismology finds it. But pure iron requires a ~ 1000 ° C impossible to free up to freeze. If it was so cooled, the whole nucleus would have been frozen, unlike the observations of seismologists.
The addition of silicon and sulfur, which suggests meteorites and seismology could be present in the nucleus, only worse – requiring even more super -referral.
Our new research explores the effect of carbon in the nucleus. If 2.4% of the nucleus mass was carbon, around 420 ° C surfing would be necessary to start freezing the inner nucleus. This is the first time that the gel of the nucleus has been possible. If the nucleus carbon content was 3.8%, only 266 ° C surfilage is required. It’s still a lot, but much more plausible.
This new discovery shows that although seismology can reduce possible chemistry from the nucleus to several combinations of different elements, many of them cannot explain the presence of the solid internal nucleus in the center of the planet.
The nucleus cannot be made only of iron and carbon because the seismic properties of the nucleus require at least one more element. Our research suggests that it is more likely to contain a little oxygen and perhaps also silicon.
This marks a significant step towards understanding what the nucleus is done, the way it started to freeze and how it has shaped our planet from the inside.
This published article is republished from The conversation Under a creative communs license. Read it original article.
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