In-Situ Mass Spectrometry of Interstellar Dust in Space Missions: A Novel Approach to Study the Physical and Chemical Properties of the Local Interstellar Cloud

Remote-sensing spectroscopy of interstellar absorption lines towards nearby stars allows us to infer the elemental composition of dust in the Local Interstellar Cloud (LIC), whereas in-situ mass spectrometry of LIC dust entering the heliosphere directly determines the composition. These two approaches are, therefore, highly complementary to each other in constraining elemental abundances in both gaseous and solid phases of the LIC. In this review, we present a comprehensive synthesis of current knowledge on the composition of the LIC derived from remote-sensing gas measurements and in-situ and laboratory dust measurements. We demonstrate that the chemical composition of LIC dust measured in situ acts as a promising tool to determine the gas-phase abundances and ionization states of the elements inaccessible through spectroscopic observations. We also show that the isotopic dust composition can be estimated by in-situ mass spectrometry and provides key information on the age of dust and gas in the LIC. The identification of the smallest dust size in in-situ data gives a clue about the magnetic field vector of the LIC and the structure of the heliospheric boundaries. In-situ data on the mass and spatial distributions of LIC dust in combination with dust dynamics calculations are accounted for by dust coagulation growth in the interstellar medium. In light of the ongoing IMAP mission and the forthcoming DESTINY + mission, in-situ mass spectrometry of LIC dust is emerging as a powerful tool for probing the physical and chemical properties of the LIC.