Gold, also known as Au, is arguably the most coveted element on Earth. It is the 79th element on the periodic table, and is used in everything from jewelry to technology. Gold has been used as a symbol for wealth and high societal status since the dawn of civilization; leaders from ancient Egyptian pharaohs to modern-day tyrants Napoleon to Hitler have placed gold in high regard throughout their regimes. Even today, real gold watches, earrings, and other pieces of jewelry are a marking of wealth. The high value of gold stems from its rarity; we have already mined over 90% of available gold on Earth, and there will not be any new gold once we run out either (Koop 2019). This is because gold is not naturally made on Earth, it actually comes from outer space!
In order to fully understand how gold is made, neutron stars must be explained first. When most large stars experience a supernova, the core of the stars will most likely collapse into itself, causing a black hole. In rare cases though, when the size of the star is “between about 1 and 3 solar masses,” it forms enough neutrons to halt the collapsing process. What is left is called a neutron star (NASA 2017). These stars are extremely small since they only consist of the core of the star, but also extremely dense. For context, the physical size of the star can be compared to the size of New York City, but its weight is about 500,000 times the weight of Earth. Essentially, the mass of the entire star is crushed and condensed to fit within an extremely small surface area. This causes the pressure within the neutron star to be extremely strong, allowing elements with high masses like gold and platinum inside the neutron star to form (NASA 2017).
Even rarer than the production of a neutron star is the chance of two neutron stars entering into a binary system. A binary system is when two stars enter into orbit of each other, growing closer and closer over the span of millions or even billions of years and eventually colliding. This collision causes enough gold “to fill 100 trillion oil tankers” to spew out into space (Achenbach 2013). Gold is not the only heavy element produced in this process either; the collision of two neutron stars on average causes seven times more platinum than gold to be released as well. At this period, though, these heavy elements only exist as dust particles within space, not solid pieces of gold or platinum. A neutron star collision only happens once every 100,000 years in the Milky Way (Achenbach 2013).
Most of the accessible gold we have on Earth today most likely comes from meteorites that struck Earth after the formation of its core. Although there was a sizable amount of gold predicted to be present during Earth’s initial creation, this gold is trapped in the core of the Earth and would not be within reach of our current mining capabilities. Scientists believe that the gold we are able to mine today comes from meteorites from the asteroid belt in between Earth and Mars. These meteorites struck down on Earth after the formation and cooling of the inner layers of Earth, allowing some gold to settle in the outer mantle and crust. This is the gold that we mine today (Kremer 2013).
Since, as previously mentioned, 90% of the extractable gold has already been mined on Earth, miners are now looking to outer space for new gold (Koop 2019). Starting in 2019, NASA has been observing the asteroid 16 Psyche, which contains an estimated 700 quintillion dollars worth of precious metals. Scientists plan to use a technique called biomining, which uses microbes and water to extract precious metals from rock (Nelson, Zehnder 2020). Biomining and other technologies in development are potentially huge advances in science and ecology; we would be able to acquire critically needed resources for consumer goods on Earth without further damaging the environment through mining. This would therefore allow us to continue to technologically progress as a society while maintaining environmental sustainability.
Works Cited:
Achenbach, J. (2013, July 17). Origin of gold is likely in rare neutron-star collisions. Retrieved July 26, 2020, from https://www.washingtonpost.com/national/health-science/origin-of-gold-found-in-rare-neutron-star-collisions/2013/07/17/a158bd46-eef2-11e2-bed3-b9b6fe264871_story.html
Koop, F. (2019, February 22). How Gold is made and how it got to our planet. Retrieved July 26, 2020, from https://www.zmescience.com/science/how-gold-is-made-science-064654/
Kremer, W. (2013, September 19). Does gold come from outer space? Retrieved July 29, 2020, from https://www.bbc.com/news/magazine-22904141
NASA. (2017, March). Neutron Stars, Pulsars, and Magnetars – Introduction. Retrieved July 27, 2020, from https://imagine.gsfc.nasa.gov/science/objects/neutron_stars1.html
Nelson, J., & Zehnder, J. (2020, January 15). Mining for Gold in Space. Retrieved July 29, 2020, from https://www.colorado.edu/coloradan/2019/10/01/mining-gold-space
Origin of Gold 