Characterizing cometary dust grains with polarimetry
Authors: Guirado Daniel , Muñoz Olga , Frattin Elisa , Gómez Martín Juan Carlos , Martikainen Julia A. , Moreno Fernando , Jardiel Teresa , Peiteado Marco , Caballero Amador C. 
Published: September 2022

&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Light scattering experiments have been carried out at visible light for two kinds &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;of dust samples: narrow size distributions consisting of low-absorbing particles &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;with sizes in the micron domain, plus millimeter-sized single grains. The polari&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;metric analysis of the scattered light has revealed as a very precise tool for size &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;characterization of the samples of particles in the resonance regime, while it let &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;us distinguish the compact/fluffy structure feature of particles much larger than &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;the wavelength.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;First, four narrow size distributions of forsterite particles, spanning a broad &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;range of scattering sizes in the resonance regime, were measured. Forsterite is &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;a Mg-rich olivine representative of low-absorbing cosmic dust particles that has &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;been identified in several comets, e.g. 1P/Halley, Hale&amp;#8211;Bopp, 9P/Tempel and &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;81P/Wild2 (see [1] and references therein). The maximum of the degree of lin&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;ear polarization (DLP) decreases with the size of the particles. That maximum &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;occurs around 90&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;&amp;#186;&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;in all cases, but the angle ranges from 75&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;&amp;#186;&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;to 140&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;&amp;#186;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;, increasing &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;with the grain size [2]. Furthermore, dust particles with size parameters from &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;&amp;#8764;&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;6 to&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;&amp;#8764;&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;20 seem to be responsible for the negative polarization branch (NBP). &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;This is in agreement with the idea that the NBP might be caused by coherent &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;back-scattering by wavelength-scaled features of the grains (see .e.g. [3]).&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;On the other hand, millimeter-sized particles were identified to reproduce &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;the flux curve of Fomalhaut protoplanetary disk [4]. Light scattering was then&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;measured for the same kind of grains in an attempt to reproduce the comet &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;67P/Churyumov-Gerasimenko phase function obtained&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;in situ&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;by the OSIRIS&lt;/span&gt;&lt;br role=&quot;presentation&quot; /&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;camera system onboard the ESA Rosetta mission. In that case it was found that &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;large porous particles with organic inclusions can reproduce both, ground-based &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;observations of the DLP and the OSIRIS phase functions [5].&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&amp;#160;&lt;/p&gt;
&lt;p&gt;&lt;strong&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;References&lt;/span&gt;&lt;/strong&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;1. Frattin, E., Mu&amp;#241;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;oz, O., Moreno, F., Nava, J., Escobar-Cerezo, J., Gomez Martin, J.C., &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Guirado, D., Cellino, A., Coll, P., Raulin, F., Bertini, I., Cremonese, G., Lazzarin, &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;M., Naletto, G., Forgia, F.L.: Experimental phase function and degree of linear &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;polarization of cometary dust analogues. Monthly Notices of the Royal Astronomical &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Society&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;484&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;, 2198&amp;#8211;2211 (2019)&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;2. Mu&amp;#241;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;oz, O., Frattin, E., Jardiel, T., G&amp;#243;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;mez-Mart&amp;#237;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;n, J.C., Moreno, F., Ramos, J.L., &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Guirado, D., Peiteado, M., Caballero, A.C., Milli, J., M&amp;#233;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;nard, F.: Retrieving dust &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;grain sizes from photopolarimetry: An experimental approach. The Astrophysical &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Journal Supplement Series&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;256&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;(17 (12pp)) (2021)&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;3. Muinonena, K., Penttil&amp;#228;, A., Videen, G.: Polarimetry of Stars and Planetary Systems, chap. Multiple Scattering of Light in Particulate Planetary Media. Cambridge University Press, Cambridge (2015)&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;4. Mu&amp;#241;oz, O., Moreno, F., Vargas-Mart&amp;#237;n, F., Guirado, D., Escobar-Cerezo, J., Min, M., Hovenier, J.W.: Experimental phase functions of millimeter-sized cosmic dust grains. The Astrophysical Journal 846(85 (8pp)) (2017)&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;5. Mu&amp;#241;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;oz, O., Moreno, F., G&amp;#243;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;mez-Mart&amp;#237;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;n, J.C., Vargas-Mart&amp;#237;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;n, F., Guirado, D., &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Ramos, J.L., Bustamante, I., Bertini, I., Frattin, E., Markannen, J., Tubiana, C., &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Fulle, M., G&amp;#252;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;ttler, C., Sierks, H., Rotundi, A., Corte, V.D., Ivanovski, S., Za&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;kharov, V.V., Bockel&amp;#233;&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;e-Morvan, D., Blum, J., Merouane, S., Levasseur-Regourd, &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;A.C., Kolokolova, L., Jardiel, T., Caballero, A.C.: Experimental phase function and &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;degree of linear polarization curves of millimetersized cosmic dust analogs. The &lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;Astrophysical Journal Supplement Series&lt;/span&gt; &lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;247&lt;/span&gt;&lt;span dir=&quot;ltr&quot; role=&quot;presentation&quot;&gt;(19 (13pp)) (2020)&lt;/span&gt;&lt;/p&gt;