At the Earth’s crust, the temperatures remain relatively cool all year round. However, beneath all crust-dwellers’ feet is an incredibly hot place. Earth’s core is believed to exceed temperatures higher than the surface of the sun – over 10,000 degrees Celsius.
[Image Source: Wikipedia]
Many years ago, billions of rocks collided and stuck together in our solar system. They continuously collided over thousands of years into the forming planet, eventually forming what would later become known as Earth. With each collision came a little more energy, causing our planet to heat up.
Some of the heat still remains from the formation of the planet nearly four and a half billion years ago. To this day, nearly 6,500 km beneath the crust, the core of the Earth continues to pump out heat from the residual heat. However, a number of factors are at play.
The heat comes from both residual heat that still exists from the formation of the planet, as well as from the nuclear fuel that naturally exists within its interior.
The core is incredibly hot, but just how much longer can its fuel supplies sustain the heat until the Earth fizzles out?
Scientists at the University of Maryland claim they will be able to answer the question within the next eight years.
Driving Earth’s tectonic plate movement and powering its magnetic field requires an immense amount of power. The energy is derived from the center of the Earth, but scientists are certain its core is slowly phasing out.
What makes the center of the Earth hot?
Keeping the center of the Earth hot are two sources of power: primordial energy left over from the formation of the planet and nuclear energy that exists because of natural radioactive decay.
The formation of the Earth came at a time when the solar system was brimming with energy. During the its infancy, meteorites constantly bombarded the forming planet causing excessive amounts of frictional force. At the time, Earth was rife with volcanic activity.
Since the beginning, the planet has cooled significantly. However, residual heat from the formation of Earth remains.
Although the primordial heat has largely dissipated, another form of heat continues to warm the mantle and crust of the Earth.
Naturally radioactive materials exist in large quantities deep in the Earth with some residing around the crust. During the natural decay process of the radioactive material, heat is released.
In combination with primordial heat and natural radioactive decay, the Earth’s core remains at an incredibly high temperature – over 10,000 degrees. Unfortunately, the heat produced from both sources is running out.
Scientists know heat flows from Earth’s interior into space at a rate of about 44 × 1012 W (TW). What they do not know, however, is how much of the heat is primordial. The issue is that if the Earth’s heat is predominantly primordial, then it will cool off significantly quicker. However, if the heat is created mostly in part due to radioactive decay, then the Earth’s heat will likely last much longer.
Why it is important
Earth’s core keeps the temperature stable, but more importantly, it prevents the atmosphere from being stripped off by solar wind.
At the center of the our planet is a massive solid iron core that rotates. Its rotation gives off a massive magnetic field that extends into space. The field holds charged particles in place that are mostly collected from the solar wind.
The fields create an impenetrable barrier in space that prevents the fastest, most energetic electrons from reaching Earth. The fields are known as the Van Allen belts, and they are what enables life to thrive on the surface of the Earth.
This animated Gif represents the Van Allen belts that deflect and absorb high energy electrons, preventing them from reaching Earth. [Image Source: NASA/Goddard/Scientific Visualization Studio]
The collection of charged particles deflects and captures the solar wind preventing it from stripping the Earth of its atmosphere. Without it, our planet would be barren and lifeless.
It is believed that Mars once had a Van Allen belt that protected it too from the Sun’s deadly wind. However, once the core cooled, it lost its shield, and now it remains a desolate wasteland.
How long will the Earth’s fuel last
Currently, many scientific models can estimate how much fuel remains to drive the Earth’s engines. The results, however, greatly differ making a final conclusion difficult to draw. At the moment, it is unknown how much primordial and radioactive energy remain.
“I am one of those scientists who has created a compositional model of the Earth and predicted the amount of fuel inside Earth today,” said one of the study’s authors William McDonough, a professor of geology at the University of Maryland. “We’re in a field of guesses. At this point in my career, I don’t care if I’m right or wrong, I just want to know the answer.”
However, researchers believe with modern technological advancements, a more accurate prediction can be made.
To determine how much nuclear fuel remains in the Earth, the researchers will use advanced sensors to detect some of the tiniest subatomic particles known to science—geoneutrinos. Geoneutrinos particles are the byproducts generated from nuclear reactions that take place within stars, supernovae, black holes and human-made nuclear reactors.
Detecting how much fuel is left
Detecting the antineutrino particles is an immensely difficult task. Massive detectors the size of a small office building buried over a kilometer down into the Earth’s crust. The depth seems overkill, however, it is necessary to create a shield from cosmic rays that can result in false positives.
In operation, the detector can detect antineutrinos when they collide with hydrogen atoms inside the apparatus. After the collision, two bright flashes can be detected, unequivocally announcing the event.
By counting the number of collisions, scientists can determine the number of uranium and thorium atoms that remain inside of our planet.
Unfortunately, the detectors KamLAND in Japan and Borexino in Italy only detect about 16 events per year, making the process painstakingly slow. However, with three new detectors projected to come online in 2020- the SNO+ detector in Canada and the Jinping and JUNO detectors in China – researchers expect more than 500 more detected events per year.
“Once we collect three years of antineutrino data from all five detectors, we are confident that we will have developed an accurate fuel gauge for the Earth and be able to calculate the amount of remaining fuel inside Earth,” says McDonough.
The Jinping detector in China is over four times bigger than all the detectors to date. Although the detector is big, the JUNO detector will remain a staggering 20 times bigger than all existing detectors.
“Knowing exactly how much radioactive power there is in the Earth will tell us about Earth’s consumption rate in the past and its future fuel budget,” said McDonough. “By showing how fast the planet has cooled down since its birth, we can estimate how long this fuel will last.”