Measuring the processing of organic and mineral cosmic dust grains with the Interstellar Dust Experiment (IDEX) instrument

The Interstellar Dust Experiment (IDEX) is a dust impact ionization Time-of-Flight (ToF) mass spectrometer launched onboard the Interstellar Mapping and Acceleration Probe (IMAP) on September 24, 2025. IMAP is in nominal science operations at the Sun-Earth Lagrange Point L1, with IDEX passively collecting cosmic dust grains at a cadence of roughly one interplanetary particle per week. IDEX will detect and analyze both Interstellar Dust Grains (ISDs) from the Local Interstellar Medium (LISM) as well as Interplanetary Dust grains (IDPs). ISD collection will begin in April 2026 as we enter the interstellar dust focusing season. IDEX will collect a variety of ISDs and IDPs over its lifetime, ranging from pristine to heavily processed particles that are a mixture of mineral and organic material.

We investigate how IDEX can be used to determine the degree of processing dust grains have undergone. These studies inform the analysis of IDEX flight data representative of organic and mineralogical cosmic dust grains. Assessments of aromaticity and the presence of functional groups can be used to determine the processing of organic species. Polycyclic aromatic hydrocarbons (PAHs) are the most pristine organic compounds. PAH destruction and processing lead to the production of heterocyclic compounds and decreasing aromaticity in organic species. Minerals can be appraised via the degree of serpentinization and conversion from crystalline to amorphous silicates. IDEX's large effective area combined with high mass resolution (m/dm > 200) and dynamic range make it well suited to assess minute variations in mass spectra pointing to pristine versus processed materials. Various campaigns from the last two years build and support the techniques presented here to analyze IDEX flight data.