(3200) Phaethon polarimetry in the negative branch: new evidence for the anhydrous nature of the <i>DESTINY</i>+ target asteroid

Geem, Jooyeon; Ishiguro, Masateru; Takahashi, Jun; Akitaya, Hiroshi; Kawabata, Koji S.; Nakaoka, Tatsuya; Imazawa, Ryo; Mori, Fumiki; Jin, Sunho; Bach, Yoonsoo P.; Jo, Hangbin; Kuroda, D.; Hasegawa, Susumu; Yoshida, Fumi; Ishibashi, Ko; Sekiguchi, T.; Beniyama, Jin; Arai, Tomoko; Ikeda, Yuji; Shinnaka, Yoshiharu; Granvik, Mikael; Siltala, L.; Djupvik, Anlaug A.; Kasikov, Anni; Pintėr, V.; Knudstrup, Emil

doi:10.1093/mnrasl/slac072

Cited by 9 publications

(2 citation statements)

References 43 publications

(65 reference statements)

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“…Phaethon's mid-infrared spectrum does not exhibit any transparency features that may be expected from volumetric scattering of fine-grained silicates [48,49,52,64] and the large spectral emissivity contrast of ∼8% is likely a result of a large thermal gradients from a coarse-grained or boulder-rich surface [62]. The absolute reflectivity of CY chips at 0.55 µm of around 10% are systematically brighter than their powdered counterparts [65,66] which is consistent with Phaethon's geometric albedo of 11% [29]. Phaethon's albedo lies in between the albedo distributions of Pallas collisional family members (0.10 < p V < 0.18) and other B-types (0.03 < p V < 0.10) [67].…”

Section: Discussionsupporting

confidence: 59%

Thermal decomposition as an activity driver of near-Earth asteroid (3200) Phaethon

MacLennan¹,

Granvik²

2022

Preprint

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Phaethon is an active asteroid with a dust tail repeatedly observed over the past decade for ∼3 days during each perihelion passage down to a heliocentric distance of 0.14 au [1][2][3]. The mechanism causing the activity is the subject of many investigations, and the suggested mechanisms lack clear supporting evidence [4][5][6]. Phaethon has been identified as the likely parent body of the annual Geminid meteor shower [7-10], making it one of the few active asteroids associated with a meteoroid stream. Its low albedo and B-type reflectance spectrum indicates that Phaethon's composition is similar to carbonaceous chondrite meteorites, but a connection to a specific meteorite group is ambiguous due to the lack of diagnostic absorption features [11][12][13][14][15][16]. Methods & Results: In this study, we analyze the mid-infrared emissivity spectrum of Phaethon and find that it is closely associated with the Yamato-group (CY) of carbonaceous chondrites. The CY chondrites represent primitive carbonaceous material that experienced early aqueous alteration and subsequent latestage thermal metamorphism [17][18][19]. Minerals in these meteorites, some of which we identify in Phaethon's spectrum, show evidence of thermal decomposition; notably, the dehydroxylation and transformation of phyllosilicates into poorly crystalline olivine. Additionally, sulfides and carbonates in CYs are known release S2 and CO2 gas upon heating to ∼700 • C [20][21][22]. We show that Phaethon's surface temperature during its observed window of activity is consistent with the thermal decomposition temperatures of several components in CY meteorites. Conclusion: All of these lines of evidence are strong indicators that gas release from thermal decomposition reactions is responsible for Phaethon's

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Section: Discussionsupporting

confidence: 59%

Thermal decomposition as an activity driver of near-Earth asteroid (3200) Phaethon

MacLennan¹,

Granvik²

2022

Preprint

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“…The polarimetric data were analysed in the same manner as described in Ishiguro et al ( 2022 ) for MSI data and in Geem et al ( 2022 ) for ALFOSC and HONIR data. We observed unpolarized standard stars to obtain the instrumental polarization parameters ( q inst and u inst ) and strongly polarized stars to determine the position angle offset ( θ off ≡ θ cat − θ obs ).…”

Section: Optical Polarimetrymentioning

confidence: 99%

Spectral type and geometric albedo of (98943) 2001 CC21, the Hayabusa2# mission target

Geem

Ishiguro

Granvik

et al. 2023

Monthly Notices of the Royal Astronomical Society: Letters

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We conducted optical polarimetry and near-infrared spectroscopy of JAXA’s Hayabusa2# mission target, (98943) 2001 CC21, in early 2023. Our new observations indicate that this asteroid has a polarimetric inversion angle of ∼20○, absorption bands around 0.9 and 1.9 μm, and a geometric albedo of 0.23±0.04. All these features are consistent with those of S-types but inconsistent with L-types. Based on this evidence, we conclude that JAXA’s Hayabusa2# spacecraft will explore an S-type asteroid (more specifically, an L or LL chondrite-like object) with albedo and size (0.44–0.53 km when we assume the absolute magnitude of 18.8) similar to (25143) Itokawa.

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A physical survey of meteoroid streams: Comparing cometary reservoirs

Buccongello,

Brown,

Vida

et al. 2024

Icarus

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(3200) Phaethon polarimetry in the negative branch: new evidence for the anhydrous nature of the DESTINY+ target asteroid

Cited by 9 publications

References 43 publications

Thermal decomposition as an activity driver of near-Earth asteroid (3200) Phaethon

Thermal decomposition as an activity driver of near-Earth asteroid (3200) Phaethon

Spectral type and geometric albedo of (98943) 2001 CC21, the Hayabusa2# mission target

A physical survey of meteoroid streams: Comparing cometary reservoirs

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