Extraterrestrial mining and metal processing are key goals for space exploration. Rodolfo Marin Rivera at KU Leuven and a team of scientists in materials sciences have published a new report in Scientific Reports. They conducted catalytic dissolution of metals from meteorite proxies of metal rich asteroids by using a deep eutectic solvent. (An eutectic solvent a homogeneous mixture that has a melting point lower than those of the constituents.) These solvents will be important for extraterrestrial mining because they can be designed to have a relatively low vapor pressure and can comprise organic waste products from extraterrestrial settlements.
The team investigated three types of meteorites, two chondrites and one iron meteorite. The chondrites samples contained silicates with metal-rich phases such as native alloys, sulfides, and oxides. The metallic iron-nickel and troilite formed the most abundant metal bearing phases of all three samples.
The scientists subjected all the samples to chemical micro-etching experiments with iodine and iron (III) chloride as oxidizing agents in a deep eutectic solvent which they formed by mixing choline chloride and ethylene glycol.
It is possible to create viable extraterrestrial metal extractions. The efficient use of local materials and resource recovery from space can significantly reduce the mass, cost and environmental constraints of space missions. Big metal-rich asteroids are parent bodies of iron meteorites and metal-rich carbonaceous chondrites.
These metals can provide a local source of materials to construct a human settlement in space or other extraterrestrial bodies. Near-Earth asteroids contain valuable platinum group metals and iron, nickel, and cobalt in greater quantities that found on the surface of the Earth.
The asteroid signatures were similar to the asteroid 16 Psyche which is the biggest metal-rich body in the solar system. This study investigated a proof-of-concept method to extract metals from meteorite proxies of asteroids by employing non-aqueous deep eutectic solvents.
Rivera and his team found depth and dissolution rates by analyzing the 3D topography of the etched samples, prior to and after etching. Chondrite meteorites can be characterized by diverse minerology where the olivine, pyroxene, plagioclase and kamacite minerals are most significant. The composition depends on the degree of the metamorphosis to which they were subject.
Diverse samples of chondrites contained iron-nickel alloys, iron sulfide and iron oxide minerals. They were less abundant in iron-nickel rich minerals with a higher proportion of iron sulfide. The silicate matrix consists of chondrule forming olivine and pyroxene, with traces of plagioclase feldspar.
The researchers classified chondrules of H3 chondrites petrographically into six widely dispersed chondrules. The Campo del Cielo sample for example is an iron-nickel meteorite which is entirely composed of iron-nickel rich mineral phases. Kamacite contains significant trace element components.
Rivera and his team investigated the iron and nickel mineral distributions across multiple meteorite samples. Iron was primarily hosted in silicate phases including olivine, pyroxene, and augite along with several different highly notable elements. The team investigated the catalytic oxidation of metals including superalloys, minerals, and the chemical etching of chondrite meteorites. Rivera and his team conducted additional chemical etching of the Camp del Cielo meteorites utilizing iodine and iron (III) chloride as oxidizing agents before and after chemical etching.
Rivera and his team used iron (III) chloride and iodine as oxidizing agents to solubilize metals from three meteorite proxies of near-Earth asteroids using deep eutectic solvent.
Analytical studies confirmed the chemical association of nickel with iron-rich metals phases in the original samples. The researchers further identified additional metals of interest for space technologies including traces of ruthenium and rhodium.
The use of asteroids as mineral and metal resources will provide a key step during space exploration. Further investigations will be required for viable economic activity. The proposed technology is at an embryonic stage and is very promising for metal recovery.