MINING THE ASTEROID: A DREAM NOT FAR BEING REALIZED

 MINING THE ASTEROID: A DREAM NOT FAR BEING REALIZED

 

 Nikunja Bihari Sahu

 

        In a landmark development on Sept 24, 2023, a sample weighing nearly 250g collected by a spacecraft of NASA named OSIREX REx from a small asteroid Bennu of our Asteroid Belt was successfully delivered to our  Earth for research and study by the scientists. In a novel exercise, the spacecraft did not land on the Earth, but rather released a  capsule from nearly 1,00,000 km altitude which entered the Earth's atmosphere and parachuted with reduced velocity to safely land with the sample in the Utah desert. The spacecraft, without landing on the Earth, headed for another asteroid in our Asteroid belt for further mission.  Although the sample collected was minuscule in quantity and was only meant for scientific study, the mission aroused the hope of mining precious metals like Gold and Platinum from the asteroids and ferrying them safely to the Earth for the benefit of entire humanity.

       In fact, OSIREX Rex was not the only mission to have collected the asteroid sample, but in the past the Japanese Space Agency JAXA has also succeeded in returning asteroid samples to Earth through its Hayabusa missions.  However, these were research missions and commercial missions to asteroids are a long way through considering the potential challenges of the task that include the high cost of spaceflight, unreliable identification of target asteroids and the challenges of extracting usable material in a space environment and delivering successfully to the Earth.

 What are Asteroids?

     An asteroid is a minor planet that orbits within our inner Solar System. These are rocky, metallic or icy bodies with no atmosphere and very little gravity. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter. Of the roughly 1 million known asteroids, the greatest number are located between the orbits of Mars and Jupiter, approximately within  2 to 4 AU distance from the Sun, in the main Asteroid Belt. The size of asteroids varies greatly; the largest asteroid Ceres is almost 1000 km across and qualifies as a Dwarf planet. The total mass of all the asteroids combined is only 3% that of the Earth's Moon. The majority of main belt asteroids follow slightly elliptical stable orbits revolving in the same direction as the Earth and taking from 3 to 6 years to complete a full circuit of the Sun. The asteroid 4- Vesta, due to its high reflective surface, is normally visible to the naked eye from the Earth.

There are mainly three types of asteroids, namely  C-type, S-type and M-type:

     C-type or Carbonaceous asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks and minerals. They have an average density of about 1.7 g/cm³. The C-type asteroids have a high abundance of water. C-type asteroids also have high amounts of organic carbon, phosphorus, and other key ingredients for fertilizer which could be used to grow plants in a space environment.

      The S-type or Silicate asteroids are mostly stony and made out of Iron silicates or Magnesium silicates. S-type asteroids carry little water but are more attractive because they contain numerous metals including Nickel, Cobalt, and more valuable metals, such as Gold, Platinum, and Rhodium. A small 10m size S-type asteroid could contain as much as 650,000 kg of metal with 50 kg in the form of rare metals like Platinum and Gold.

      The M-type or Metal asteroids are very interesting because some of them are thought to be the remaining cores of early planets that never ended up forming completely. They have high concentrations of metals usually Nickel and Iron. This is the type of asteroid that scientists often refer to when they talk about asteroid mining and harnessing of space resources. M-type asteroids are believed to have formed close to the Sun and they would have had to been exposed to high temperatures in their early days. Some of them might have even had iron volcanoes at some point of time. These asteroids are also the source of the metallic meteorites that sometimes reach our Earth; these meteorites are pieces that fell off after a collision of an M-type asteroid with another object. 

    A class of easily retrievable objects (EROs) was identified by a group of researchers in 2013. Twelve asteroids made up the initially identified group, all of which could be potentially mined with present-day rocket technology. Of the 9,000 asteroids searched in the Near Earth Objects (NEO) database, these twelve could all be brought into an Earth-accessible orbit by changing their velocities by less than 500 meters per second (1,800 km/h; 1,100 mph). The dozen asteroids range in size from 2 to 20 meters.

 History of Asteroid Mining

    Before 1970, asteroid mining existed largely within the domain of science fiction. Stories such as ‘ Worlds of If', 'Scavengers in Space' and 'Miners in the Sky' described the conceived dangers, motives, and experiences of miners engaged in mining the asteroids. Although scientists envisioned about the benefits that could be gained from asteroid mining, they lacked the necessary technology to seriously pursue the idea. However, with man first landing on the Moon in 1969 and successfully bringing back lunar rocks to the Earth, the ambition of asteroid mining was again aroused. Subsequently, some scientists moved away from the asteroid craze and rather thought of targeting the nearby celestial objects like the Moon, Mars and its small satellites namely Deimos and Phobos.

 

Composition of Asteroids and Why These are of Interest to Us

    Although asteroids and Earth accreted from the same starting materials, Earth's relatively stronger gravity pulled all heavy siderophilic (Iron-loving) elements into its core during its molten youth stage more than 4 billion years ago. This left the crust depleted of such valuable elements until a rain of asteroid impacts re-infused the depleted crust  with  gold, cobalt, iron, manganese, molybdenum, nickel, osmium, palladium, platinum,  rhenium, rhodium, ruthenium and tungsten among other metals. Today, these metals are generally mined from Earth's crust and form an essential stuff  for our economic and technological progress. From one point of view, it is believed that mining the asteroids would be relatively easy because, unlike our Earth,  most valuable deposits are located near the asteroid’s surface rather than near the core . But the only obstacle is to reach there!

     Even without a manned mission to do a full-scale study of an asteroid, scientists know a lot about what these bodies contain from Earth-based measurements. Astronomers use telescopic spectroscopy which analyzes light reflected from the asteroid's surface, to find out their composition. In addition to metals like  Iron, Nickel and Magnesium, scientists think Water, Oxygen, Gold and Platinum also exist on some asteroids. Water interests space explorers most, because it could help keep a space colony alive as without water, there is really no way to move ahead with human exploration of space. Water could also be broken down by the method of electrolysis using sunlight into its constituent elements such as  Hydrogen and Oxygen to form rocket engine propellant. The metals mined and extracted from the asteroids could also be used for building spacecraft and other structures for a space colony that would further ease asteroid exploration.

 Asteroid Extraction and Processing

     The drive  to set up a sustained  mining operation in place  on an asteroid is , by no means,  an easy task. While building an asteroid mine will cost billions of dollars, it will be far cheaper than carrying supplies from Earth to the Moon or Mars. Spacecraft would have to carry food and supplies for the mining crew and the equipment for mining activities. Newly developed spacecraft should make landing on an asteroid possible. After all, man has already landed on the Moon and some asteroids pass-by closer than the Moon from the Earth. A spacecraft going to an asteroid would need less rocket power and fuel than one going to the Moon. One problem will be how to keep the asteroid from rotating while it is being mined. Some experts suggest attaching rockets to the asteroid to take the spin out of it. But once miners land on the asteroid, they have to plan to dig it for minerals, process the materials extracted and transport it to a space colony orbiting around the Earth  or directly to the Earth itself. Although no one knows for sure what the first asteroid mine will look like, there are some good assumptions about them which are outlined below:

         Asteroid mining activities would involve drilling boreholes and injecting hot liquid or gas and allowing the useful materials to react or melt with the solvent and extract the solute. Due to the weak gravitational fields of asteroids, any activities, like drilling or boring, will cause large surface disturbances to eject plumes of dust clouds. These might be confined by some dome or bubble barrier, or else some means of rapidly dust  dissipating  mechanism should be provided for to get rid of these dusts. Mining operations require special equipment to handle the extraction and processing of ore in outer space. The machinery will need to be anchored to the body of the asteroid; but once in place, the ore can be moved about more readily due to the lack of gravity. However, no technique for refining ore in zero gravity conditions currently exists. Docking with an asteroid might be performed using a harpoon-like process, where a projectile would penetrate the surface to serve as an anchor; then an attached cable would be used to winch the vehicle to the surface if the asteroid is both penetrable and rigid enough for a harpoon to be effective.

    The machinery will likely to be solar-powered to reduce the need for fuel that would have to be hauled to the asteroid by a spacecraft. All the equipment should be light-weight  for easy transport to the asteroid. Most equipment will be robotic in nature  to reduce the need for manpower to carry out mining activities. This would bring down  the amount of supplies, like food and other essential items required for a long manned mission. Miners on asteroids would use techniques similar to those on the Earth. The most likely method will be  to scrape desired materials off the asteroid and tunnel into veins of specific substances. Scraping or Strip mining will pull out valuable ore that will float off the asteroid. Because much of the ore will fly off, a large canopy might be used to collect it. As the asteroids have little gravity, the mining equipment, and the astronaut miners who operate them, will have to use grapples to anchor themselves securely to the ground. However, the lack of gravity is an advantage in moving mined materials around without having to use much muscle power. Once a load of materials is ready to be sent to the Earth or to a space colony around it, rocket fuel for a ferrying spacecraft could be produced by breaking down water harvested from the asteroid into Hydrogen and Oxygen molecules. After an asteroid's minerals and resources have been completely exhausted by the mining project, the mining equipment can be shifted to another potential asteroid candidate  for further mining without bringing them back to the Earth.

 Economy of Mining

      Currently, the quality of the ore and the consequent cost and mass of equipment required to extract it are unknown and can only be speculated. Some economic analyses indicate that the cost of returning asteroid minerals to the Earth far outweighs their market value and that asteroid mining will not attract private investment at current commodity prices and space transportation costs. Other studies suggest that large profit could be made by using solar power. 

     In 1997, it was speculated that a relatively small metallic asteroid with a diameter of 1.6 km (1 mile) contains more than US$20 trillion worth of industrial and precious metals. A comparatively small M-type asteroid with a mean diameter of 1 km (0.62 mle) could contain more than two billion metric tons of Iron–Nickel ore, or 2 to 3 times the world production of 2004. The asteroid 16-Psyche is believed to contain 1.7×10¹⁹ kg of Nickel–Iron, which could supply the world production requirement for several million years. In fact, a small portion of an asteroid's extracted material would bea precious stuff  in comparison to our Earth’s standards!

       Not all mined materials from asteroids would be cost-effective, especially for the potential return of economic amounts of material to the Earth. For a potential return to Earth, Platinum is considered very rare in terrestrial geologic formations and , therefore, is potentially worth bringing some quantity for terrestrial use. Nickel, on the other hand, is quite abundant on Earth  and is mined in many terrestrial locations; hence, the high cost of asteroid mining may not make it economically viable. The development of an infrastructure for altering an asteroid’s orbit to our technically  favourable locations could make our mining activities easier and would offer a large return on investment.

        Hence, if our dream of mining the asteroids comes true, our planet Earth would be richer by many counts by plundering the asteroid wealth!

 

Education Officer

Regional Science Centre

Bhopal

Phone : 8917637974