Martha S. Hanner

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We have investigated scattering properties of aggregates , emphasizing the size of constituent monomers comparable with the wavelength of visible light, in order to model the scattering properties of cometary dust. This has differentiated our study from previous investigations of aggregates in which the size of the monomers was much smaller than the(More)
Comet Hale-Bopp (C/1995 O1) was observed at wavelengths from 2.4 to 195 micrometers with the Infrared Space Observatory when the comet was about 2.9 astronomical units (AU) from the sun. The main observed volatiles that sublimated from the nucleus ices were water, carbon monoxide, and carbon dioxide in a ratio (by number) of 10:6:2. These species are also(More)
Images taken by the Stardust mission during its flyby of 81P/Wild 2 show the comet to be a 5-kilometer oblate body covered with remarkable topographic features, including unusual circular features that appear to be impact craters. The presence of high-angle slopes shows that the surface is cohesive and self-supporting. The comet does not appear to be a(More)
Along Ulysses' path from Jupiter to the south ecliptic pole, the onboard dust detector measured a dust impact rate that varied slowly from 0.2 to 0.5 impacts per day. The dominant component of the dust flux arrived from an ecliptic latitude and longitude of 100 + 10 degrees and 280 degrees +/- 30 degrees which indicates an interstellar origin. An additional(More)
Infrared spectral properties of silicate grains in interplanetary dust particles (IDPs) were compared with those of astronomical silicates. The approximately 10-micrometer silicon-oxygen stretch bands of IDPs containing enstatite (MgSiO3), forsterite (Mg2SiO4), and glass with embedded metal and sulfides (GEMS) exhibit fine structure and bandwidths similar(More)
The debris disks surrounding the pre-main sequence stars HD 31648 and HD 163296 were observed spectroscopically between 3 and 14 m. Both possess a silicate emission feature at 10 m which resembles that of the star Pictoris and those observed in solar system comets. The structure of the band is consistent with a mixture of olivine and pyroxene material, plus(More)
We report 3-13 µm spectroscopy of 4 comets observed between August 2002 of insufficient quality to detect the presence of a silicate band of comparable strength to the other three objects, and we place an upper limit of 24% on this feature. The silicate features in both NEAT and Kudo-Fujikawa contained structure indicating the presence of crystalline(More)