The figure above shows the mass density of the solar system as a function of
distance from the Sun. The primordial density level is derived from the mass
distribution of the planets. The decrease in density from 30 to 50 AU may be
due to the scattering of material by the giant planets. Beyond 50 AU there
are no observations to constrain the level and the density may increase.
Interstellar Probe will observe the spatial density, composition, and size
distribution of dust that results from collisional processes in the Kuiper
Belt. Also under consideration is the possibility of surveying the population
of Kuiper Belt objects >1 km in size with a small telescope.
Our Solar system is thought to be the end product of a common astrophysical
process of stellar system formation from protoplanetary disk nebulae.
Collisions play a central role in the formation and evolution of planetary
systems, either increasing or eroding the mass of the bodies. The present
interplanetary dust population is a result of collisional processes occurring
in the solar system. Interstellar Probe will provide the opportunity for in
situ and infrared sensing of interplanetary and interstellar dust in the
heliosphere and the interstellar medium. These measurements will determine
the composition and the mass and orbital distributions of dust in the outer
solar system and study its creation and destruction mechanisms. It will also
be possible to search for dust structures associated with planets, asteroids,
comets, and the Kuiper Belt. These studies will constrain theories of the
collisional dynamics of the solar system and help us understand the origin
and nature of our solar system and other planetary systems as well.
Interstellar Probe can address the fundamental question of the radial extent of the primordial solar nebula, or, more precisely, the extent
of the primordial planetesimal disk. This can be accomplished most directly by measuring the variation with heliocentric radius of the
population of small bodies in the Kuiper Belt, or, less directly, by measuring the radial variation of the spatial density of dust grains
derived from Kuiper Belt objects. Moreover, the Kuiper Belt is an analog for circumstellar disks around other stars. Improved
understanding of its properties will aid in the interpretation of astronomical observations of planet-forming or planet-harboring disks
around other stars.