PDS: The Planetary Atmospheres Node
Cover Page/Proposal Summary
ROSS-99 NRA 99-OSS-01
Date Due: 5/3/99
|
This proposal shall be used and disclosed for evaluation purposes only, and a copy of this Government notice shall be applied to any reproduction or abstract thereof. Any authorized restrictive notices that the submitter places on this proposal shall also be strictly complied with. Disclosure of this proposal for any reason outside the Government evaluation purposes shall be made only to the extent authorized by the Government. |
| Proposal Type: New Proposal |
| Proposal Category: Comets |
| Major Equipment Proposal? No |
| Do you intend to submit an Education/Public Outreach (E/PO) proposal? No |
| Proposal Title: |
| Complex silicate grains with sublimating mantles: A systematic laboratory study of optical properties and application to cometary observations |
| Abbreviated Proposal Title: |
| Optics of sublimating dust applied to comets |
| Principal Investigator: |
| Dr. Ludmila Olegovna
Kolokolova Department of Astronomy Laboratory for Astrophysics University of Florida 211 Bryant Space Sciences Center P.O. Box 112055 Gainesville, FL 32611-2055 Phone: 352-392-2287 Fax: 352-392-5089 E-mail: ludmilla@astro.ufl.edu |
| Signature | Date |
| _____________________________________ | ____________ |
| Co-Investigators and Collaborators: | |||
| Type | Name | Affiliation | |
| Sci Co-I | Prof. Bo A. S. Gustafson | University of Florida | gustaf@astro.ufl.edu |
| Sci Co-I | Dr. Martha S. Hanner | Jet Propulsion Laboratory, NASA | msh@scn1.jpl.nasa.gov |
Proposal Summary:
The unique microwave analog facility for the study of light-scattering at the University of Florida allowed us to obtain angular and spectral properties of model dust particles using analogue materials and precisely known grain geometries. We found that for aggregates of silicate/organic constituent particles, a likely kind of cometary dust grains, the wavelength dependencies of intensity (color) and polarization (polarimetric color) are sensitive to the presence of organic material. We applied the results to observational data for comet Hale-Bopp (Gustafson & Kolokolova, J. Geoph. Res., 1999) to uncover new evidence for the sublimation/disintegration of an organic dust component. We are now proposing a systematic investigation into the dependence of optical properties of the model cometary particles (silicate aggregates covered by an organic or icy mantle) on the composition and thickness of the mantle. The dependence of intensity and polarization in red and blue wavebands on the mantle will be obtained for a variety of sizes and compactness of the aggregates. Thus, changes in light scattering that are indicative of the sublimating material will be found. The combination of the laboratory data with now available high-quality photometric and polarimetric cometary images in red and blue dust filters (Jockers et al., Proc. Conf. on Hale-Bopp, Tenerife, January 1998) allows studies of the evolution of cometary dust with the distance from the nucleus. From this, we will estimate the rate of evaporation of organic materials and/or ices in real comets. The corresponding sublimation constants for cometary organics/ices will narrow the range of possible compounds and will help identify the compounds. The data on change in optical properties with sublimation have broad applicability and will be made available for use in modeling of haze and aerosol particles in planetary atmospheres, including Mars, giant planets, and Titan as well as for cometary dust.
