Experimental phase function and degree of linear polarization of cometary dust analogues

Abstract

We present experimental phase function and degree of linear polarization curves for seven samples of cometary dust analogues namely: ground pieces of Allende, DaG521, FRO95002 and FRO99040 meteorites, Mg-rich olivine and pyroxene, and a sample of organic tholins. The experimental curves have been obtained at the IAA Cosmic Dust Laboratory at a wavelength of 520 nm covering a phase angle range from 3 • to 175 • . We also provide values of the backscattering enhancement (BCE) for our cometary analogue samples. The final goal of this work is to compare our experimental curves with observational data of comets and asteroids to better constrain the nature of cometary and asteroidal dust grains. All measured phase functions present the typical behavior for µm-sized cosmic dust grains. Direct comparison with data provided by the OSIRIS/Rosetta camera for comet 67P Churyumov-Gerasimenko reveals significant differences and supports the idea of a coma dominated by big chunks, larger than one micrometer. The polarization curves are qualitatively similar to ground-based observations of comets and asteroids. The position of the inversion polarization angle seems to be dependent on the composition of the grains. We find opposite dependence of the maximum of the polarization curve for grains sizes in the Rayleigh-resonance and geometric optics domains, respectively.

The Gemini Planet Imager View of the HD 32297 Debris Disk

“…Therefore, we expect that the true SPF of HD 32297 declines more steeply at the largest scattering angles than we measure here. On the other hand, if the polarisability curve is symmetric about 90 • (as seen in cometary dust, e.g., Frattin et al 2019), this effect would cancel out when Figure 8. H-band SPF (left) and polarisability curve (right) of the HD 32297 disk, using the best estimate of the ring geometry.…”

Photometry, spectroscopy, and polarimetry of distant comet C/2014 A4 (SONEAR)

“…10) that Titan's tholin had the necessary photopolarimetric properties for particles larger than 1 µm. holins as a component of cometary material has been already considered in a number of publications starting from pioneering papers by Sagan & Khare (1979, and other papers by those authors) and up to the papers related to interpretation of the Rosetta data (e.g., Stern et al 2015;Poch et al 2016;Frattin et al 2019). Besides, Bonnet et al (2015) showed that IOM (insoluble organic matter) found in carbonaceous meteorites and also considered as the organic component in the Rosetta dust (Bardyn et al 2017) could originate from tholin-like organics.…”

An Exo–Kuiper Belt with an Extended Halo around HD 191089 in Scattered Light

“…The halo is likely both more forward-and backward-scattering in the probed scattering angles. previous measurements (e.g., Perrin et al 2014;Frattin et al 2019;Milli et al 2019). To better constrain the polarized fraction values, we need H-band total intensity observations to rule out the wavelength-dependent effect.…”