"Demon Nickel", come back to Earth with me!

Last week, under the influence of the current tension between Russia and Ukraine, an "epic short squeeze" event occurred in the international financial market. The price of a relatively niche metal "nickel" on the London Metal Exchange rose by 250% in two trading days, breaking the historical record. This hot financial event was dubbed the "demon nickel" market by many media. Now, let us cross the universe of billions of years and explore the past and present of the "demon nickel".

01 The name "Demon Nickel" is innate

Nickel (Ni), element number 28 in the periodic table, is a silvery-white metal with a melting point of 1453 °C and a boiling point of 2732 °C. Due to its similar atomic structure and chemical properties, it is collectively called the "iron group elements" with iron (Fe) and cobalt (Co).

Nickel metal | Source: Internet

In the 17th century, German copper miners had been trying to extract copper from a dark red ore with a green coating on the surface, but they were unsuccessful. In desperation, they named it "kupfernickel", which means "fairy copper". In 1751, Swedish mineralogist and chemist Axel Fredrik Cronstedt first separated metallic nickel from the ore and named it Nickel after the naughty fairy in the German miners' legend (similar to the English nickname for the devil, "Old Nick").

Red arsenic nickel ore (Kupfernickel) | Source: Internet

It is worth mentioning that cobalt, a close relative of nickel, was discovered and named by Kronstedt's teacher, Swedish chemist George Brandt, from cobaltite (cobalt arsenide sulfide); and the name Cobalt comes from the German word "kobold", which means "little fairy". Because nickel and cobalt ores often contain arsenic (As), highly toxic arsenic trioxide (arsenic) will be released during the smelting process, seriously threatening the health of workers. So in this sense, both "demon nickel" and "demon cobalt" can be said to be "true to their names"!

02 Where does the “demon nickel” come from?

Let's go back to the beginning of the universe 13.8 billion years ago and see how the elements that make up this colorful world were produced. According to the Big Bang theory of the origin of the universe, within hundreds of seconds of the Big Bang, protons and neutrons synthesized hydrogen, helium and a very small amount of lithium. In 1957, the Burbidges, Fowler and Hoyle published the famous B2FH theory, which believed that other elements were synthesized by a series of processes such as stellar burning, slow neutron capture (s process), and fast neutron capture (r process) on the basis of the primordial hydrogen and helium produced by the Big Bang. Inside a massive star, light elements continue to fuse, and the combustion of hydrogen, helium, carbon, neon, oxygen, and silicon occurs from the outside to the inside, until an iron-nickel nucleus is formed; while elements with larger atomic numbers may be formed in supernova explosions, binary neutron star mergers and other events.

Schematic diagram of nuclear reactions and layer structures inside red giant stars | Source: Internet

Although scientists are still constantly improving, expanding and perfecting the B2FH theory, it is certain that most of the elements that make up our solar system have been gradually synthesized through multiple rounds of stellar evolution.

The origin of the elements in the solar system. Nickel originates from the explosion of white dwarfs and the nuclear synthesis process inside massive stars. | Image source: SDSS.org

03 "Demon Nickel Base Camp"

Since the chemical composition of CI carbonaceous chondrites (except for a few volatile elements) is very close to that of the solar photosphere, they are often used to approximately represent the average composition of the entire solar system. Based on this, the average nickel content of the solar system is about 1.1 wt%; while the average nickel content of the earth's crust is only 80 ppm, less than one percent of the average content of the solar system. So where did the "demon nickel" go?

To explore this question, we need to go back to the birth of the solar system 4.6 billion years ago to understand the melting differentiation of planets. This refers to the process of planet formation, when the heat energy generated by the decay of radioactive nuclides causes the constituent materials to melt; because of the immiscibility of metal and silicate melts, the denser iron-nickel metal "sinks" to form a metallic core, while the lighter silicate part "floats up" and evolves into the structure of the shell and mantle. Obviously, the core is the "demon nickel base camp" on Earth, and most of the nickel elements on Earth are in the core.

Schematic diagram of the core-mantle-crust structure of a terrestrial planet | Source: Modified from the Internet

Millions of miles from Earth, the asteroid belt between Mars and Jupiter is home to millions of asteroids, many of which are metallic asteroids. In addition to the cores of the giant planets, the solar system is home to another "nickel powerhouse" in the solar system. Iron meteorites are samples from metallic asteroids, and their nickel content can be as high as 5 wt% to 17 wt%. Iron meteorites are mainly composed of iron-nickel metals and their sulfides, phosphides, etc., and often present a characteristic Vickers-Teden structure under acid corrosion. Because iron-nickel alloys have good corrosion resistance and ductility, ancient people thousands of years ago began to use meteorite iron to make weapons and labor tools.

Vickers-Teden structure of the Carbo iron meteorite | Source: Modified from Meteorites & the Early Solar System II

04 Catch that "demon nickel"!

Nickel is an important industrial metal with huge demand in industries such as steel, machinery, construction and chemicals. However, the reserves of nickel in the earth's crust are limited, and the mining of nickel ore has caused many negative impacts on the earth's ecological environment. In order to protect the earth's natural resources and environment, people have begun to turn their attention to the development and utilization of space resources. NASA plans to explore an asteroid 16 Pysche (Psyche) with a diameter of about 200 kilometers, which is composed of iron-nickel metals and precious metals such as platinum and gold. It is estimated that the asteroid is worth more than 100 trillion US dollars. Even if it is divided equally among 8 billion people on earth, it can make everyone a "millionaire".

Conceptual image of the exploration of asteroid 16 Psyche | Source: NASA

Over the past decade, dozens of domestic and foreign companies have been committed to the research and development of asteroid mining technology. Although the technology is not yet mature, with the development of human society, the development and utilization of space resources will be the general trend. Let us boldly imagine that in the future, space mining robots will cruise freely in the asteroid belt, find the target asteroid rich in iron and nickel, and grab it, "Demon nickel, come back to Earth with me!" I believe that in the near future, such imagination will become a reality!

Hypothetical image of space mining | Source: DeepSpaceIndustries

Author profile: Wang Ying, associate researcher at the Astrochemistry and Planetary Science Laboratory, Purple Mountain Observatory, Chinese Academy of Sciences, research area: meteorite science and astrochemistry.

(This article was first published on the WeChat public account "Shanghai Planetarium")

Rotating Editor-in-Chief: Su Yang

Editor: Wang Kechao