Pair 1 is incorrectly matched: The Cassini-Huygens mission was a joint NASA/ESA/ASI mission to study the planet Saturn and its system of rings and moons. The Huygens probe successfully landed on Saturn's largest moon, Titan. Pair 2 is correctly matched: The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) was a NASA spacecraft that orbited the planet Mercury from 2011 to 2015, studying its chemical composition, geology, and magnetic field. Pair 3 is correctly matched: These twin NASA spacecraft were launched in 1977 to conduct a "Grand Tour" of the outer planets. They provided detailed images and data on Jupiter, Saturn, Uranus, and Neptune and are now continuing their journey into interstellar space.