NEBULA DUST: PRIMITIVE GRAIN AGGREGATES OR RECONDENSED? Collaborators: Ashley Espy, Univ. of Florida Ludmilla Kolokolova, Univ. of Maryland Yu-Lin Xu, NASA/JSC Bo Gustafson

PRIMITIVE GRAIN AGGREGATES “COMETARY?”

RECONDENSED “ASTEROIDAL-ZODIACAL?”

THE MICROWAVE ANALOGUE LABORATORY AT THE UF

Silicate and organics in Visual = Plastics in Microwave ADVANTAGES / LIMITATIONS - Analogue materials are grey - One particle, one geometry at a time - Systematic Investigations - Scaling = NO APPROXIMATION

Scattering Angle [Degrees] Intensity Color Scattering Angle [Degrees] Color through Red and Blue Filters Blue color is usually not observed.

Denser = redder. Dust aggregates need not be dense or very large for interaction to be important Scattering Angle [Degrees] Intensity Color Scattering Angle [Degrees] Color through Red and Blue Filters

1 micron Denser = redder. Dust aggregates need not be dense or very large for interaction to be important HOW COLOR IS CREATED: INTERACTION VOLUME DEPENDS ON WAVELENGTH

Scattering Angle [Degrees] Polarization Polarimetric Color Scattering Angle [Degrees] Polarization through Red and Blue Filters Polarimetric color for cometary dust is red but blue for zodiacal light.

Scattering Angle [Degrees] Polarization Polarimetric Color Scattering Angle [Degrees] Polarization through Red and Blue Filters Polarimetric color for cometary dust is red but blue for zodiacal light. Can be cometary but not Zodiacal

Scattering Angle [Degrees] Intensity Color Scattering Angle [Degrees] Color for cometary dust and zodiacal dust is mostly red.

Scattering Angle [Degrees] Intensity Color Scattering Angle [Degrees] Larger = redder. Color for cometary dust and zodiacal dust is mostly red.

Scattering Angle [Degrees] Polarization Polarimetric Color Scattering Angle [Degrees] Still looks like cometary dust (red)

Scattering Angle [Degrees] Intensity Color Scattering Angle [Degrees] Color for cometary dust and zodiacal dust is mostly red.

Scattering Angle [Degrees] Intensity Color Scattering Angle [Degrees] Look redder Color for cometary dust and zodiacal dust is mostly red.

Scattering Angle [Degrees] Polarization Polarimetric Color Scattering Angle [Degrees] Polarimetric color for cometary dust is red but blue for zodiacal light.

Scattering Angle [Degrees] Polarization Polarimetric Color Scattering Angle [Degrees] Polarimetric color for cometary dust is red but blue for zodiacal light. Look bluer

K isotherm [AU]  Sphere “Comet” aggregate

CONCLUSIONS - Interactions inside aggregates generate colors - “Asteroid” / “comet” particles differences in polarimetric color - Micron scale structure in aggregates may preserve memory of aggregation processes - Large aggregates can behave as though they were made of larger substructures than they really are. - “Asteroid” / “comet” particles trends are as observed

Scattering Angle [Degrees] Intensity Color Scattering Angle [Degrees] Look redder Color for cometary dust and zodiacal dust is mostly red.

Scattering Angle [Degrees] Polarization Polarimetric Color Scattering Angle [Degrees] Polarimetric color for cometary dust is red but blue for zodiacal light.

Scattering Angle [Degrees] Polarization Polarimetric Color Scattering Angle [Degrees] Polarimetric color for cometary dust is red but blue for zodiacal light.