Should we love or hate space rocks?
Listen to The Golden Age by The Asteroids Galaxy Tour, Space Rock by Rockets, Space Rock by Trip Rexx, and Lucy in the Sky with Diamonds by The Beatles to fully enjoy reading this post.
Asteroids are rocks spread over the Solar System, orbiting around the Sun, the big attractor. Why are they there? In a few words, planets formed from a primordial cloud of gas and dust orbiting around our star, aggregating because of gravity. Not all material ended up creating large planets, but some of it remained scattered out there forming smaller items, like dwarf planets (such as lovely Pluto) and, of course, asteroids.
To give you an example, think about a LEGO construction. Asteroids are like leftover pieces once you finish the construction: you completed the project following the instructions (the planets), but those pieces remained in your hands (the asteroids). As well as those LEGO pieces, asteroids can be useful for building something else! This idea is behind asteroid mining, a theoretical concept that has become increasingly concrete in recent years.
Before rushing to it, let’s look closely at our space nuggets, to understand better why mining them could be a great opportunity. First of all, they are categorized according to their composition, into three major types:
- C-type or carbonaceous, the most common, are very dark objects containing mainly carbon, clay, silicate rocks, and even a good percentage of water in the form of hydrated minerals and ice, like a dirty chunk of stone coal;
- S-type or silicaceous, proper stones that are made up mainly of silicate materials based on iron and magnesium;
- M-type or metallic, the most rare and desirable nuggets, made mainly of nickel-iron minerals, often accompanied by other precious metals, such as gold, platinum, and rare earths.
In addition to these three main groups, several subcategories, some consisting of a single asteroid, differ from all the others.
Another way to classify asteroids is based on their position in the Solar System. We have:
- Near Earth Asteroids, or NEA, are objects whose circles around the Sun sometimes bring them close to the Earth’s orbit and to the Earth itself; they are divided, in turn, into subcategories depending on the shape of their orbit (Amor, Apollo, Aten);
- Trojans, are special objects, parked in particular points of a major planet orbit (Lagrange points), allowing them to follow or precede at the same distance from the planet itself during its trip around the Sun; the name “Trojans” was chosen because the first discovered asteroids in this group were identified with the names of heroes from Homer’s Iliad; the most numerous are Jupiter’s ones;
- Main Belt Asteroids, located between the orbit of Mars and Jupiter, form the largest group of this classification, and they are what remains of a planet that never formed or exploded in the very early stages of its formation (there is still no definitive theory about it, even if nowadays the “never formed planet” is the most accredited);
- Centaurs, small groups of objects that are spread out between Jupiter and Neptune, more similar in composition to comet nuclei (more ice than minerals);
- Kuiper Belt Objects, or Trans-Neptunian Objects (TNO), are large groups over Neptune’s orbit, full of frozen stony objects but even dwarf planets like Pluto.
What about the Oort Cloud? Isn’t there a group of asteroids in the great suburbs of our Solar System? The answer is “We don’t know yet”. The Oort Cloud is so far away that scientists are unsure what it is made of. Only occasionally we have been in contact with the “visitors” coming from there, the long-period comets. This is why the Oort Cloud is known as the House of Comets.
By the way, keep an eye on the object known as 2014 UN 271. It comes straight from the Oort Cloud and should reach the closest point to the sun in its orbit (called perihelion) in 2031. Some space agencies may send a probe to study it because it is exceptional also for its size (between one and three hundred kilometers!).
At this point another question could arise: is there a relationship between comets and asteroids? They are like cousins, belonging to the same kind of cosmic fragments. However, there are differences: comets are almost like dusty snowballs, while asteroids are like stones, as seen above. Comets are also characterized by having a coma and one (or more) trail, while asteroids do not exhibit such features.
They could also differ in their orbit shape which is usually more eccentric and elongated for comets. On the other hand, sometimes the distinction between comets and asteroids can become very “subtle”, and there are objects that can even move from one group to the other, like Centaurs themselves.
Let’s keep comets aside for now and ask the following question: How do we know all this about our beloved rocks?
Scientists have been observing asteroids with telescopes of all kinds since the Italian astronomer Giuseppe Piazzi discovered, Ceres, on January 1, 1801. Since then, more than a million asteroids have been found, analyzed, and cataloged. Despite running for two centuries, the task of discovering asteroids is just at the beginning: it is estimated that in the Solar System, there are hundreds of millions of asteroids larger than one meter!
We didn’t just observe asteroids with telescopes, we also sent spacecraft to visit them closely, and even touch them. NASA probe Galileo made the first fly-by of an asteroid during its trip to Jupiter and its moons in 1991. The spacecraft passed a few thousand miles from 951 Gaspra, a gorgeous stony asteroid in the Main Belt, taking the first incredible closeups of this new world.
The first mission entirely dedicated to studying an asteroid was NEAR Shoemaker, a spacecraft full of instruments that scanned 433 Eros, a huge stony NEA, king of records: the first NEA discovered, first orbited, and first even touched by a spacecraft.
Other very enthralling missions have been the European Rosetta, which orbited and touched Comet 67P/Churyumov-Gerasimenko (remember to bear comets in mind!), and the Japanese Hayabusa, which was able to return to Earth a small sample of another stony NEA, 25143 Itokawa.
On December 6, 2020, the Japanese Hayabusa-2 sent a bigger sample of carbonaceous NEA 162173 Ryugu back to Earth, with a spectacular re-entry of the sample capsule over the Australian desert. On September 24, 2023, another spacecraft returned a sample of another NEA: NASA OSIRIS-REx visited 101955 Bennu, orbited it for almost three years, collected an impressive amount of scientific data, touched the surface, and delivered back a 250-gram sample.
Now that we know a little more, let’s explore how asteroids could be both the potential incipit of our journey amongst the stars and its very end!
Since the discovery of Ceres, astronomers have become increasingly good at identifying asteroids and predicting their orbits. All this information was and is currently registered by the Minor Planet Center (MPC), “the single worldwide location for receipt and distribution of positional measurements of minor planets, comets and outer irregular natural satellites of the major planets”.
It is the official asteroidal registry office. One of its major tasks is to calculate the orbits of newly identified objects and to warn about the risk of their potential future impact on our planet. So, the MPC will be the first to wave the flag in case of a possible collision threat, the real “dark side” of our space nuggets.
How can such adorable cosmic pebbles turn into deadly space bombs? The dinosaurs learned it the hard way: the impact of a huge asteroid, some kilometer in diameter, blew away their habitat and existence. Scientists found great evidence of this event, the Chicxulub Crater is a clear witness.
In 2013, we were luckier, as we experienced “only” the explosion of a tiny twenty-meter-large asteroid in the atmosphere thirty kilometers over Chelyabinsk: no casualties, but more than one thousand people were injured and seven thousand buildings were damaged.
If the first example is a very unfrequent event, one every hundred million years, the second one is more common, and Chelyabinsk’s impact hadn’t been predicted before it happened! This circumstance rang the bell and the UN decided to manage the question more seriously: it created the International Asteroid Warning Network.
This international group was tasked with developing a well-defined strategy to assist Governments in analyzing the consequences of asteroid impacts and planning mitigation responses. After that decision, NASA reorganized its observation programs and established the Planetary Defense Coordination Office, with the mission to coordinate the efforts to plan responses to these potential impact threats.
Similarly, other organizations came to light or increased their activities, like the B612 Foundation (B612, the name of the tiny world of The Little Prince!), created with “the goal to protect the Earth from asteroid impacts”, and the Asteroid Day initiative, aimed at raising the awareness of the asteroid threat.
Out of curiosity, the UN officially established Asteroid Day at the end of 2016. Since then it has been celebrated on the 30th of June, the anniversary of another historical impact, the Tunguska impact (in 1908 over the Siberian forest of Tunguska, thousands of trees were flattened, a huge number of reindeer were killed and windows were blown hundreds of miles away due to an asteroid impact with the atmosphere).
As you can see, the asteroid threat is serious business, not just stuff for science-fiction blockbusters like Armageddon or Deep Impact (too much fiction than science, to be honest). Is there anything that could be done? Is there any way to manage such a menace?
As said, the first step is to discover, measure, and track potentially hazardous objects (mainly Near Earth Asteroids or NEA) with multiple observations to calculate their future orbits more accurately. The second step is to assess the impact risk. For this purpose, scientists developed the so-called Torino Scale (similar to the Richter Scale for earthquakes), which combines the probability and damage on a scale from 0 to 10 (0 business as usual, 10 adieu world).
The record so far is a level 4 on the Torino scale, obtained in December 2004 by 99942 Apophis, a 240-meter-wide stony NEA. Its first measurements led to the prediction of a possible devastating impact on the Earth in 2029. Thanks to further observations, it was downgraded to level 0 for 2029 and level 1 for 2036 encounters.
Although there are no risks for an impact, Apophis close encounter is an exceptional event and will be the object of several studies, some from the Earth’s surface and some in space. The OSIRIS-APEX (APophis EXplorer) is the new mission for the OSIRIS-REx spacecraft which has already met the asteroid Bennu (see above). ESA is planning a mission in space too: the Rapid Apophis Mission for Space Safety (RAMSES) will be launched in April 2028 and will reach Apophis just in time to witness the fly-by.
About future encounters, two missions launched in the last years and are on their way to their final destination: Lucy (are you listening to the song suggested at the beginning? Yes, its name is linked to it!), the first mission to Jupiter’s Trojan asteroids, and Psyche, aimed to study the possible remnant of the metal core of the planet not formed between Mars and Jupiter, the biggest metallic asteroid of the Solar System, 16 Psyche.
Discovering, tracking, and qualifying are the first steps to managing such a threat. Then, the Rendez-vous missions added and will add precious scientific information to understand their composition, shape, and structure.
However, it’s not enough. To be ready for an eventual collision of a huge asteroid, we need the planetary defense missions!
The American DART and the European HERA were the first missions developed to test a possible defense strategy. The two spacecraft have the common objective of understanding if playing pool in space with asteroids works as a defense action, not only as a spectacular celestial game.
DART spacecraft, the white cue ball, launched on November 24, 2021, aboard a SpaceX Falcon 9 rocket, the stick. DART reached asteroid 65803 Dydimos and its moon, Dimorphos, the colored ball, on September 26, 2022. On the same day, the half-ton spacecraft aimed straight at Dimorphos, and hit it at more than 24.000 Km/h with a perfect stroke!
And HERA? To quantify how many points DART scored, placing Dymorphos in a different orbit around Dydimos, HERA will play the referee role counting the score of DART’s stroke. It launched in October 2024 and, some years later, it will reach the Dydimos system, observing all the changes produced by the impact.
LICIA Cube, an Italian cubesat brought by DART to the game table, witnessed that the blow had been struck. The following observations from Earth have estimated the changes to Dymorphos’ orbit. However, HERA will collect precious information on the game scene to develop the first effective defense strategy: playing cosmic snooker!
Apropos of space games, a trendy virtual amusement played by many people could be applied to space: Minecraft. For those who have never heard of it, in Minecraft’s world, the player must collect an incredible variety of resources, combine and use them to build almost everything, limited only by the imagination. It’s a game of discovery and creativity, leading to incredible adventures, a true time stealer.
Having said that, how could we play Minecraft in space? Combining two promising space technologies, asteroid mining, and space manufacturing, could create the perfect game set.
As seen above, asteroids are made of diverse materials, from ice to carbon, siliceous minerals, and metal ores. Some could be used to build space structures, and others could provide the basic elements to fuel spacecraft or even support human life in space. It would be only a matter of collecting, processing, and bringing the materials where needed. This is the basic concept of asteroid mining: extract resources from these space quarries to use them for any purpose.
How far are we from making this concept real? Several studies have already been undertaken on the matter and many others are ongoing. Startups and companies are already building prototypes and proof of concepts. Let’s see some of them.
Trans Astronautica Corporation, or TransAstra in short, is a perfect example. Led by the experienced technical pioneer Joel Sercel, the TransAstra engineering team is working on an innovative mining method, called Optical Mining. Thanks to the use of solar energy, which is plentiful in space, this technology allows the extraction of raw material by hitting a rock with a concentrated ray of light and fracturing it into tiny pieces. The optical mining device will be mounted on a special spacecraft called Honey Bee. The idea is to fly to an asteroid, up to 40 meters in diameter, cover it with a big bag, and hit it with concentrated sun rays. The little fragments, water, and other volatiles will then be collected in the wrapping bag.
The California-based startup, Astroforge, has ambitious plans to mine asteroids for precious metals, particularly platinum-group metals (PGMs). They aim to mine those materials in space at a lower cost than terrestrial mining. In April 2023, they launched their first mission to demonstrate their metal refining technology in orbit. The Brokkr cubesat was a useful testbed to identify weaknesses in the satellite design, that will be improved for their next mission to a Near Earth asteroid in 2025.
Another strategy that looks very promising is using microbes to modify rocks and extract materials, or, in a single word, biomining. Even if this technique has been well known for decades, a new experiment called BioRock was recently installed on the International Space Station, providing important results on extracting rare earths from rocks in microgravity. In the future we could recruit armies of microbes, to obtain raw materials useful for our expansion into space, not only for asteroid mining but also for In-Situ Resource Utilization (ISRU) on the Moon, Mars, and all other rocky satellites.
Okay, plenty of raw materials will be available in space sooner or later without requiring costly launches from Earth. But how can we use them?
Here comes the space manufacturing process. It involves the production of different goods in the space environment, from construction elements to specific tools and even electronic parts.
In collaboration with the private company Redwire Corporation, NASA ran a program to develop in-space manufacturing capabilities, called OSAM-2. They were able to print an object in space in 2014, thanks to a special 3D printer installed on the ISS, and they also developed a machine to produce optical fibers in microgravity, resulting in much better quality than the ones made on the Earth’s surface. They placed on the ISS a module to print ceramic materials, the Ceramic Manufacturing Module, which performed successfully the first test in early December 2020.
Mixing asteroid mining and space manufacturing, we could realize in space the infrastructures we need to live there, without depending so much on the precious terrestrial materials. In a few words, we could become real space Minecrafters!
So, we went through a lot of information about our dear space nuggets: categorizations, exploration missions, frightening threats, cosmic snooker, space Minecrafters… As you have just seen, they could be our cross, in case of an impact on our planet. But they could also be our delight, thanks to their precious resources, which could end the current economy of scarcity and be used to create the bricks for our new homes in space and the tiles to pave the road to becoming Spacepolitans.
Becoming Spacepolitans 