Where are Interstellar and Interplanetary Dust Particles from?

Interstellar and interplantary dust particles come in a variety of compositions and sizes. The primary source of these cosmic dust grains is the interstellar medium. In the interstellar medium, the particles are cycled through evolutionary processes with the formation of giant molecular clouds, protosuns, planetary systems, comets, and other debris objects. Comets, asteroids, and meteroids bring these cosmic dust particles into the interplanetary medium. For example, the zodiacal light, which is the visibly scattered sunlight by dust, is believed to originate from interplanetary dust particles with diameters in the 5 - 100 micron range.

Purpose of this experiment:

The purpose of this experiment is to focus on direct laboratory measurements of the infrared scattering properties of common interstellar and interplanetary dust particles in the 1-25 micron spectral region. This includes studying extinction coefficients, polarization characteristics, and the scattering phase function. Also DIRBE infrared data will be examined for determination of dust particle physical characteristics and distributions in the interplanetary medium by using infrared models and inversion techniques.

Approach:

The same experimental technique used to study dust charging mechanisms will be used for this investigation. Single dust grains of interplanetary and interstellar composition and physical types will be irradiated, and the scattered radiation intensity measured as a function of angle. The observed data will be analyzed by fitting Mie theory calculations of intensities as a function of the scattering angle, for the determination of the particle diameter, the complex refractive index, the extinction coefficients, the phase function, and the induced polarization of the scattered intensity.

Future Plans:

Includes observations and measurements of rotational bursting of circumsolar type dust particles and nucleation and condensation of volatile / icy constituents on suspended dust grains in simulated planetary / interstellar cloud environments.