Bacteria: a good helper for space mining

The earth’s resources are depleting

  Human consumption of natural resources exceeds the rate of resource regeneration, and the self-cleaning ability of the natural environment cannot keep up with the rate of human pollution. According to historical data released by the US environmental protection agency “Global Ecological Footprint Network”, in the 1960s, most countries in the world showed ecological surplus, and it was not until the 1970s that the “Earth Overdraft Day” began to appear. The concept of “earth overdraft” was first proposed by the “Global Ecological Footprint Network”, which means that within a year, human consumption of the earth’s natural resources exceeds the total amount of earth’s natural resources regenerated. “Earth Overdraft Day” is uncertain. As the population continues to increase, human consumption of natural resources is also increasing, and the “Earth Overdraft Day” is advanced every year. Since 1986, about every 10 years, the “Earth Overdraft Day” will arrive one month earlier. For example, the “Earth Overdraft Day” in 1993 was October 21, and in 2003 was September 22. The “Earth Overdraft Day” in 2018 is August 1, and 2019 is advanced to July 29, becoming the earliest “Earth Overdraft Day” in history. In other words, starting from July 29, 2019, the resources used by humans in that year have been “borrowed” from 2020. The continuous advancement of the time when the total annual resources are used up reflects the increasing demand for natural resources by mankind. The continuous overdraft of future natural resources has damaged the earth’s biological capacity. At the current rate of consumption, the resources of 1.75 earths are needed every year to meet human needs. If mankind wants to achieve a balance between the consumption of earth’s natural resources and the total amount of earth’s natural resources regeneration by 2050, the “Earth Overdraft Day” will be delayed by 5 days every year in the future.

The asteroid “16Psyche” is a large metal body composed of iron, nickel and rare metals (including gold, platinum and copper).

  Excessive and unreasonable development of mineral resources has a negative impact on the earth’s ecological environment. Relevant data show that according to the current human estimates of the earth’s resources, the remaining resources will be exhausted only if they can be used by humans for a few hundred years. For example, most of the gold fell deep underground when the earth was formed. At present, some gold mines in the world have been mined to a depth below 3.6 kilometers above the ground, which is difficult and costly to mine. Up to now, the world’s proven reserves of major metallic and non-metallic mineral resources are 145 billion tons. Calculated at the current mining speed, the available life for copper, aluminum, nickel and tin is 22 years, 164 years, and 77 years, respectively. And 28 years, many non-renewable rare metal resources can only be used by humans for 10 years. Take platinum as an example. All the platinum metal in the world will be used up within 15 years. This kind of rare metal cannot be synthesized, and once it is used up, there will be no way to obtain it. The same thing has happened to many other rare metals. With the continuous consumption of mineral resources, 44 endangered elements will be in short supply on the earth in the future.
How much do you know about space treasures

  The moon, Mars, and many asteroids are rich in metals, which makes it possible for humans to continue to obtain rare metals that are mainly used in the manufacture of electronic devices and other products. They are hard to find on the earth, and the number of some of them is almost unlimited in space. Scientists envision that some day in the future, all heavy industries and mining industries will “move to space” and only activities related to life will be carried out on the earth.
  With the current level of science and technology, in order to realize space mining, we must first choose a good planet for mining. The moon is a transfer station for future human exploration of space. Scientists analyzed lunar craters through the lunar exploration orbiter and found that there are high levels of iron and titanium under the moon, which are estimated to reach an astonishing trillion tons. The data collected by the “Apollo Moon Landing Program” previously showed that the total amount of “helium-3” resources on the moon reached 1 million to 5 million tons, and “helium-3” is a next-generation highly efficient , Clean, safe and cheap nuclear fusion fuel for power generation. In addition, researchers have used neutral gas and ion mass spectrometers to detect iron, magnesium, and sodium ions in the upper atmosphere of Mars. This is the first time in history that there is conclusive evidence that metal ions can persist on another planet outside the Earth. superior.

In the “biological rock” experiment, astronaut Luca Palmitano put the “biological excavation reactor” device into a centrifuge on the International Space Station.

  In addition to Mars and the Moon, the asteroid’s rich mineral and metal reserves are also very eye-catching. Asteroids refer to celestial bodies in the solar system that move around the sun and resemble planets but are much smaller in volume and mass than planets. 98.5% of asteroids are located in the asteroid belt between the orbits of Mars and Jupiter in the solar system. There are 120,437 asteroids that have been numbered in this rather vast area. According to the structure, asteroids can be divided into S-type, C-type and M-type. Among them, the main components of S-type asteroids are silicate minerals and a large amount of ice; C-type asteroids are composed of carbonaceous compounds and water ice; the number of M-type asteroids is not as large as the first two, but their main components are Pure metal.
  Take the mysterious asteroid “16Psyche” as an example. It has a diameter of more than 200 kilometers and a distance of about 370 million kilometers from the Earth. It is a large metal body composed of iron, nickel and rare metals (including gold, platinum, and copper). M-type asteroids. According to estimates, the total value of “16Psyche” metal exceeds the total value of all currencies in circulation in the world. NASA plans to launch an unmanned probe to visit the asteroid “16Psyche” in 2022. Researchers believe that it may be the exposed core of an early planet. Planets including the Earth have metal cores deep in the rock. If scientists’ guesses are correct, exploring this asteroid will help them understand how planets or other celestial bodies were layered in the early formation process, such as the formation of the Earth’s core, mantle, and crust.
Good biological mining effect

  If humans want to further explore the solar system and establish settlements on other moons and planets, they need to find a way to mine minerals and metals in situ. Scientists are studying the feasibility of biological mining in space. Biological mining technology has good prospects. Its basic principle is to put ore into a container filled with water and bacteria, and use bacteria to extract specific metals contained in the rock. Bacteria participate in the natural weathering and destruction of rocks, releasing the minerals contained in them, and at the same time help to purify contaminated soil. Bio-mining completely relies on the natural action of biological organisms to better extract minerals from low-grade ores and tailings that were previously considered unusable. Although it takes longer than traditional mining, because it does not require mechanical operations for crushing ore, the operating system is relatively simple and requires less funding, which is particularly beneficial for mining deep veins and low-grade ore.

  Biological mining includes two different extraction techniques: biological leaching and biological oxidation. The traditional method of extracting copper from copper ore relies on the use of toxic chemicals at extremely high temperatures, which can cause environmental damage and diseases. Currently, approximately 20% of the world’s copper is extracted from bioleaching. People dump low-grade ore in a “leaching pile” and soak the ore with a weak sulfuric acid washing solution. Next, the acid reaction with the ore sulfide matrix promotes the growth of Thiobacillus ferrooxidans, which degrades the ore and releases metal or mineral deposits. The mineral-rich liquid is collected and separated, and the remaining sulfuric acid can be reused for the next leaching cycle. The biological oxidation law is widely used to extract gold from gold-bearing refractory ores. This process can reduce the dependence on cyanide in gold mining. According to statistics, 5% of the earth’s gold is mined using bacteria.
  For more than ten years, a research group led by astrobiologist Charles Cocker at the University of Edinburgh in the United Kingdom has been developing new technologies that use bacteria for mining operations on the Moon or Mars. They designed a device the size of a small matchbox called a “biomining reactor” that can be easily transported and installed on the International Space Station. Each biomining reactor contains a bacterial solution in which a small piece of basalt containing mineral elements that can be broken down by microorganisms is immersed in the solution.
  At the end of July 2019, the experiment called “Biological Rock” by Charles Cocker’s research team arrived at the International Space Station on the “Dragon” spacecraft of the US Space Exploration Technology Company to conduct a low-Earth orbit experiment. Scientists used 18 bio-mining reactors to test the feasibility of bacteria mining in space in microgravity and even non-gravity environments. In order to clarify the efficiency of bacteria extracting 14 different rare earth elements from basalt, and whether it can produce the same weathering effect on the rocks on the moon or Mars, the astronauts of the International Space Station have identified Sphingomonas, Bacillus subtilis and Copper Bacillus The separated solutions were placed in simulated Martian gravity, simulated earth gravity and microgravity environments for experiments, and used three weeks to evaluate the biological exploitation potential of three different bacteria under different gravity conditions. While experimenting on the International Space Station, controlled experiments under ordinary gravity conditions were also carried out on Earth.
  The results of the study show that only Sphingomonas leached rare earth elements from basalt under the three gravitational states, which can increase the effective extraction rate of minerals in the biological mining reactor by 111.9% to 429.2%. Among them, cerium and neodymium, which are the most abundant in rare earth elements, have the highest leaching rate, reaching 70%. However, Bacillus subtilis and Bacillus greedy copper both exhibit reduced leaching efficiency or unable to extract rare earth elements at all under low gravity. This shows that although the bio-mining ability of bacteria is biologically specific, this ability can continue to exist in space and Martian-like gravity conditions to help humans find materials necessary for survival in space.
  The “biological rock” experiment has provided support for the feasibility of biological mining technology in the entire solar system. It is believed that this technology can help humans play a greater role in colonizing other planets in the future.