First results of the Interplanetary Dust Experiment (IDEX) onboard the Interplanetary Mapping and Acceleration Probe (IMAP) Mission.

Launched in September 2025, NASA’s Interstellar Mapping and Acceleration Probe (IMAP) now operates at the Sun–Earth L1 Lagrange point to investigate the interaction between the heliosphere and its interstellar environment. Among its ten-instrument payload is the Interstellar Dust Experiment (IDEX), which is designed to measure the flux, size distribution, and chemical, elemental, and isotopic composition of dust particles entering the solar system.

IDEX directly samples interstellar dust (ISD) originating in the local interstellar medium (LISM), providing unique insight into the composition of contemporary interstellar solid matter. A key scientific objective is to assess whether the present-day LISM dust population is compositionally consistent with the primordial material from which the solar system formed. In addition to ISD, IDEX measures interplanetary dust particles (IDPs) of cometary and asteroidal origin, including grains that may preserve pre-solar molecular cloud material as well as particles altered by solar system processing. These observations enable comparisons between interstellar, cometary, and asteroidal dust and help constrain the origins and evolutionary histories of organic-rich materials.

IDEX measurements of the directional and size distributions of ISD provide critical constraints on models of dust transport through the heliosphere, including the filtering effects of heliospheric magnetic fields and solar activity on small, charged grains. These data contribute to improved understanding of the heliospheric boundary and the processes governing the penetration of dust into the inner heliosphere.

IDEX is an impact-ionization time-of-flight mass spectrometer that analyzes ions generated by high-velocity dust impacts on a target surface. This presentation provides an overview of IDEX’s scientific objectives and measurement capabilities and reports on early in-flight performance and initial results, demonstrating IDEX’s role in linking interstellar and solar system material populations.