Scientists still have much to learn about what small asteroids are made of. These rocky bodies may contain valuable metals, ancient material left over from the formation of the solar system, and chemical clues that reveal the history of their original parent bodies. Because of this, they are increasingly viewed as possible sources of future space resources.
A research team led by the Institute of Space Sciences (ICE-CSIC) examined samples linked to C-type asteroids, carbon rich objects that are believed to be the original sources of carbonaceous chondrites. Their results, published in the Monthly Notices of the Royal Astronomical Society, strengthen the case that these asteroids could serve as important material reservoirs. The findings also help scientists identify where these meteorites came from and support planning for future space missions and resource extraction technologies.
Carbonaceous chondrites arrive on Earth naturally, but they account for only about 5% of all meteorite falls. Many are extremely fragile and break apart before they can be recovered, which makes them especially rare. When they are found, it is often in desert environments such as the Sahara or Antarctica, where preservation conditions are favorable.
"The scientific interest in each of these meteorites is that they sample small, undifferentiated asteroids, and provide valuable information on the chemical composition and evolutionary history of the bodies from which they originate," says Josep M. Trigo-Rodríguez, the study's lead author and an astrophysicist at ICE-CSIC, affiliated to the Institute of Space Studies of Catalonia (IEEC).
To carry out the study, the ICE-CSIC team selected and carefully characterized asteroid related samples before sending them for detailed chemical analysis. The measurements were performed using mass spectrometry at the University of Castilla-La Mancha by Professor Jacinto Alonso-Azcárate. This work allowed the researchers to determine the precise chemical makeup of the six most common types of carbonaceous chondrites and assess whether extracting materials from their parent asteroids could one day be practical.
The Asteroids, Comets, and Meteorites research group at ICE-CSIC has spent more than a decade studying the physical and chemical properties of asteroid and comet surfaces. "At ICE-CSIC and IEEC, we specialize in developing experiments to better understand the properties of these asteroids and how the physical processes that occur in space affect their nature and mineralogy," Trigo-Rodríguez explains.
He also notes that ICE-CSIC serves as the international repository for NASA's Antarctic meteorite collection. Over the past ten years, he has helped select and request several of the carbonaceous chondrites used in this study and has designed multiple experiments around them. "The work now being published is the culmination of that team effort," he says.
Are Asteroid Resources Worth Extracting?
"Studying and selecting these types of meteorites in our clean room using other analytical techniques is fascinating, particularly because of the diversity of minerals and chemical elements they contain. However, most asteroids have relatively small abundances of precious elements, and therefore the objective of our study has been to understand to what extent their extraction would be viable," says Pau Grèbol Tomás, a predoctoral researcher at ICE-CSIC.
Jordi Ibáñez-Insa, a co-author of the study and researcher at Geosciences Barcelona (GEO3BCN-CSIC), points out that while many small asteroids are covered in loose surface material known as regolith, collecting small samples is very different from extracting resources at scale. "Although most small asteroids have surfaces covered in fragmented material called regolith -and it would facilitate the return of small amounts of samples-, developing large-scale collection systems to achieve clear benefits is a very different matter. In any case, it deserves to be explored because the search for resources in space could be susceptible to minimizing the impact of mining activities on terrestrial ecosystems," he says.
The main asteroid belt contains an enormous range of objects, and understanding what resources they hold requires careful classification. According to Trigo-Rodríguez, asteroid composition varies widely due to their long and complex histories. "They are small and quite heterogeneous objects, heavily influenced by their evolutionary history, particularly collisions and close approaches to the Sun. If we are looking for water, there are certain asteroids from which hydrated carbonaceous chondrites originate, which, conversely, will have fewer metals in their native state. Let's not forget that, after 4.56 billion years since their formation, each asteroid has a different composition, as revealed by the study of chondritic meteorites."
One key conclusion of the research is that mining undifferentiated asteroids -- the primordial remnants of the solar system's formation considered the progenitor bodies of chondritic meteorites -- remains impractical for now. However, the team identifies a different class of relatively pristine asteroids that display olivine and spinel signatures as more promising mining targets.
To confidently identify such candidates, the researchers emphasize the importance of detailed chemical studies of carbonaceous chondrites combined with new sample return missions. These missions would help confirm which asteroids are truly linked to the meteorites studied on Earth.
Technology, Water, and Long Term Exploration
"Alongside the progress represented by sample return missions, companies capable of taking decisive steps in the technological development necessary to extract and collect these materials under low-gravity conditions are truly needed. The processing of these materials and the waste generated would also have a significant impact that should be quantified and properly mitigated," Trigo-Rodríguez adds.
The team expects progress in the near future, especially as in situ resource use becomes increasingly important for long duration missions to the Moon and Mars. Using materials found in space could significantly reduce the need for supplies launched from Earth. If water is the primary target, the researchers stress that asteroids altered by water and rich in water bearing minerals should be prioritized.
Extracting resources in low gravity environments will require entirely new approaches. "It sounds like science fiction, but it also seemed like science fiction when the first sample return missions were being planned thirty years ago," says Pau Grèbol Tomàs.
Globally, several concepts are already being discussed, including capturing small asteroids that pass close to Earth and placing them into circumlunar orbit for study and resource use. Trigo-Rodríguez highlights that water rich carbonaceous asteroids may be especially attractive targets. "For certain water-rich carbonaceous asteroids, extracting water for reuse seems more viable, either as fuel or as a primary resource for exploring other worlds. This could also provide science with greater knowledge about certain bodies that could one day threaten our very existence. In the long term, we could even mine and shrink potentially hazardous asteroids so that they cease to be dangerous," he explains.