DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains

Details DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains

Oct 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dps....42.2838l&link_type=abstract

American Astronomical Society, DPS meeting #42, #28.38

Statistics

Computation

Scientific paper

An analysis of the Spitzer IRS spectra of the Deep Impact ejecta of comet 9P/Tempel 1 (Wooden et al. 2010, 42nd DPS Meeting) in conjunction with the dynamics of the ejecta grains (Kelley et al. 2010, 42nd DPS Meeting) strongly suggests that ecliptic comets have comae dominated by large (> 10 - 20 micron in radii) porous grains with Mg-rich crystal inclusions. In fact, Kelley et al. (2010) conclude that many ecliptic comets may be dominated by such grains with a high crystalline fraction, approximately 40% by mass, despite their generally weak silicate emission feature. To date, no model for the optical properties in the mid-IR of multi-mineralic large porous grains with silicate crystal inclusions, has been performed. We have initiated a program to compute the absorption and scattering efficiencies for these grains. Presented here are the 3 - 40 micron absorption efficiencies for models of sub-micron sized crystalline forsterite grains of irregular shape. We use the Discrete Dipole Approximation (DDA) to create discrete targets of forsterite that can be included in large porous aggregates. Computations are performed on the NAS Pleiades supercomputer. Our calculated absorption efficiencies for individual grains of forsterite are in agreement with laboratory measurements (Tamanai et al. 2006; Koike et al. 2003) and the continuous distribution of ellipsoids (CDE) method by Harker et al. (2007). We find for discrete grains that grain shape has a strong effect on the peak location of a crystalline resonance and that mimicking the physical properties of forsterite is important. Also presented are the absorption efficiencies for simple multi-component aggregates and for collections of forsterite crystals of different size and shape to replicate laboratory samples.
This research is supported by the NASA GSRP Program.

Affiliated with

Also associated with

No associations

Rating

DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and DDA Modeling for the Mid-IR Absorption of Irregularly Shaped Crystalline Forsterite Grains will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1122773