Reflection, emission, and polarization properties of surfaces made of hyperfine grains, and implications for the nature of primitive small bodies

Sultana, Robin; Poch, Olivier; Beck, Pierre; Schmitt, Bernard; Quirico, E.; Spadaccia, Stefano; Patty, Lucas; Pommerol, Antoine; Maturilli, Alessandro; Helbert, Jörn; Alemanno, Giulia

doi:10.1016/j.icarus.2023.115492

Cited by 15 publications

(16 citation statements)

References 99 publications

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“…A similar magnitude of change in the polarization phase curve was produced by Sultana et al (2023) for laboratory samples by changing the ratio of olivine to FeS hyperfine grains in the sample being observed. These observations were obtained at visible wavelengths, and olivine was acting as a scattering element, while FeS was acting as an absorptive element in the optical mixture.…”

Section: Discussionsupporting

confidence: 61%

The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids

et al. 2023

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Polarization phase-curve measurements provide a unique constraint on the surface properties of asteroids that are complementary to those from photometry and spectroscopy and have led to the identification of the “Barbarian” asteroids as a class of objects with highly unusual surfaces. We present new near-infrared polarimetric observations of six Barbarian asteroids obtained with the WIRC+Pol instrument on the Palomar Hale telescope. We find a dramatic change in polarimetric behavior from visible to near-infrared for these objects, including a change in the polarimetric inversion angle that is tied to the index of refraction of the surface material. Our observations support a two-phase surface composition consisting of high albedo and high index of refraction inclusions with a small optical size scale embedded in a dark matrix material more closely related to C-complex asteroids. These results are consistent with the interpretation that the Barbarians are remnants of a population of primitive bodies that formed shortly after calcium-aluminum-rich inclusion (CAIs). Near-infrared polarimetry provides a direct test of the constituent grains of asteroid surfaces.

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Section: Discussionsupporting

confidence: 61%

The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids

et al. 2023

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“…The Reststrahlen bands can be detected as maxima or minima, depending on the interplay between volume and surface scattering (Emery et al 2006). Many factors can alter scattering regimes: hyperfine opaques (Sultana et al 2023), regolith porosity (Martin et al 2022), different salts (Izawa et al 2021), and even environmental conditions (Donaldson Hanna et al 2017). Here, we assembled the spectra with all the Reststrahlen bands as maxima, for simplicity.…”

Section: Resultsmentioning

confidence: 99%

Ryugu’s Anhydrous Ingredients and Their Spectral Link to Primitive Dust from the Outer Solar System

Brunetto,

Lantz,

Fukuda

et al. 2023

ApJL

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Ryugu is a second-generation C-type asteroid formed by the reassembly of fragments of a previous larger body in the main asteroid belt. While the majority of Ryugu samples returned by Hayabusa2 are composed of a lithology dominated by aqueously altered minerals, clasts of pristine olivine and pyroxene remain in the least-altered lithologies. These clasts are objects of great interest for revealing the composition of the dust from which the original building blocks of Ryugu's parent asteroid formed. Here we show that some grains rich in olivine, pyroxene, and amorphous silicates discovered in one millimeter-sized stone of Ryugu have infrared spectra similar to the D-type asteroid Hektor (a Jupiter Trojan), to comet Hale–Bopp, and to some anhydrous interplanetary dust particles of probable cometary origin. This result indicates that Ryugu's primary parent body incorporated anhydrous ingredients similar to the building blocks of asteroids (and possibly some comets) formed in the outer solar system, and that Ryugu retained valuable information on the formation and evolution of planetesimals at different epochs of our solar system's history.

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“…This suggests that the parent body of rubble pile Ryugu formed far from the Sun, incorporated ices of water and carbon dioxide, and that subsequent increases in temperature caused intensive aqueous alteration to convert primary silicate phases to Mg-rich phyllosilicates and carbonates. Other phases formed by the alteration include pyrrhotite and magnetite, but they were not detected in the spectra due to the lack of diagnostic absorption bands in the wavelength range probed ( 68 , 69 ). Small Vis-NIR spectral variations among Ryugu samples can be explained by variations in sample surface texture and orientation (fig.…”

Section: Discussionmentioning

confidence: 99%

“…The matrices of Ryugu grains are rich in small pyrrhotite grains (13), which is distinct from those of Orgueil (75). Abundant opaque minerals may work as a darkening agent for Ryugu samples, considering that previous studies have shown that the addition of Fe sulfide (troilite) can make the reflectance spectrum of silicate (forsterite) darker and blue-sloped (69,76). Abundant tiny sulfides can be a precursor of sulfate veins found in CI chondrites (13,56,57), and Ca sulfates might have been derived from alteration of Ca carbonates and sulfides in Orgueil (13) S10C) (49,58).…”

Section: Comparison Of Ryugu Samples and Unheated CI Chondritesmentioning

confidence: 99%

Reassigning CI chondrite parent bodies based on reflectance spectroscopy of samples from carbonaceous asteroid Ryugu and meteorites

Amano,

Matsuoka,

Nakamura

et al. 2023

Sci. Adv.

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The carbonaceous asteroid Ryugu has been explored by the Hayabusa2 spacecraft to elucidate the actual nature of hydrous asteroids. Laboratory analyses revealed that the samples from Ryugu are comparable to unheated CI carbonaceous chondrites; however, reflectance spectra of Ryugu samples and CIs do not coincide. Here, we demonstrate that Ryugu sample spectra are reproduced by heating Orgueil CI chondrite at 300°C under reducing conditions, which caused dehydration of terrestrial weathering products and reduction of iron in phyllosilicates. Terrestrial weathering of CIs accounts for the spectral differences between Ryugu sample and CIs, which is more severe than space weathering that likely explains those between asteroid Ryugu and the collected samples. Previous assignments of CI chondrite parent bodies, i.e., chemically most primitive objects in the solar system, are based on the spectra of CI chondrites. This study indicates that actual spectra of CI parent bodies are much darker and flatter at ultraviolet to visible wavelengths than the spectra of CI chondrites.

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Reflection, emission, and polarization properties of surfaces made of hyperfine grains, and implications for the nature of primitive small bodies

Cited by 15 publications

References 99 publications

The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids

The Increasingly Strange Polarimetric Behavior of the Barbarian Asteroids

Ryugu’s Anhydrous Ingredients and Their Spectral Link to Primitive Dust from the Outer Solar System

Reassigning CI chondrite parent bodies based on reflectance spectroscopy of samples from carbonaceous asteroid Ryugu and meteorites

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