Researchers have taken the first steps toward finding liquid solvents that may someday help extract critical building materials from lunar and Martian-rock dust, an important piece in making long-term space travel possible. Using machine learning and computational modeling, researchers have found about half a dozen good candidates for solvents that can extract materials on the moon and Mars usable in 3D printing. The powerful solvents, called ionic liquids, are salts that are in a liquid state.