Phase reddening on asteroid Bennu from visible and near-infrared spectroscopy

Fornasier, S.; Hasselmann, P. H.; Deshapriya, J. D. P.; Barucci, Maria Antonella; Clark, B. E.; Praet, A.; Hamilton, Victoria E.; Simon-Miller, A. A.; Li, J.-Y.; Cloutis, E. A.; Merlin, F.; Zou, Xiao-Duan; Лауретта, Д. С.

doi:10.1051/0004-6361/202039552

Cited by 29 publications

(14 citation statements)

References 75 publications

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“…In agreement with Fig. 2, the reddest regions have the deepest band at 0.55 µm, as confirmed by Fornasier et al (2020). The 1.05-µm depth map (Fig.…”

Section: Spatial Distributionsupporting

confidence: 89%

Weak spectral features on (101995) Bennu from the OSIRIS-REx Visible and InfraRed Spectrometer

Simon-Miller

Kaplan

Cloutis

et al. 2020

A&A

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Context. The NASA Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) mission has obtained thousands of spectra of asteroid (101955) Bennu with the OSIRIS-REx Visible and InfraRed Spectrometer. Aims. We present a spectral search for minor absorption bands and determine compositional variations on the surface of Bennu. Methods. Reflectance spectra with low and high spatial resolutions were analyzed for evidence of weak absorption bands. Spectra were also divided by a global average spectrum to isolate unique spectral features, and variations in the strongest band depths were mapped on a surface shape model. The global visible to near-IR spectrum of Bennu shows evidence of several weak absorption bands with depths of a few percent. Results. Several observed bands are consistent with phyllosilicates, and their distribution correlates with the stronger 2.74-μm hydration band. A 0.55-μm band is consistent with iron oxides and is deepest in the spectrally reddest areas on Bennu. The presence of hydrated phyllosilicates and iron oxides indicates substantial aqueous alteration in Bennu’s past. Conclusions. Bennu’s spectra are not identical to a limited set of carbonaceous chondrite spectra, possibly due to compositional properties and spatial scale differences; however, returned samples should contain a mixture of common chondrite materials.

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“…In agreement with Fig. 2, the reddest regions have the deepest band at 0.55 µm, as confirmed by Fornasier et al (2020). The 1.05-µm depth map (Fig.…”

Section: Spatial Distributionsupporting

confidence: 89%

Weak spectral features on (101995) Bennu from the OSIRIS-REx Visible and InfraRed Spectrometer

Simon-Miller

Kaplan

Cloutis

et al. 2020

A&A

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“…The variation of the spectral slope with phase angle, knows as the spectral phase reddening effect, is the results of small-scale surface roughness and multiple scattering in the surface medium at extreme geometries (high phase angles) and it is commonly observed on several Solar System bodies. This has been reported for asteroids (see Fornasier et al 2020 and references therein), comets (Fornasier et al 2015, Longobardo et al 2017, as well as planets and their satellites (Gehrels et al 1964, Warell & Bergfors, 2008, Nelson et al 1987, Cuzzi et al 2002, Filacchione et al 2012. In case of a low-albedo surface, such as that of cometary nuclei, the spectral phase reddening effect has been interpreted as due to the presence of fines, namely, particles of ∼ micron size, or to the irregular surface structure of larger grains, having micron-scale surface roughness (Li et al 2019, Schröder et al 2014, Pilorget et al 2016.…”

Section: Spectral Phase Reddeningmentioning

confidence: 59%

Small lobe of comet 67P: Characterization of the Wosret region with ROSETTA-OSIRIS

Fornasier,

de Micas,

Hasselmann

et al. 2021

Preprint

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Aims. We investigated Wosret, a region located on the small lobe of the 67P/Churyumov-Gerasimenko comet subject to strong heating during the perihelion passage. This region includes the two last landing sites of the Philae lander as well as, notably the final one, Abydos, where the lander performed most of its measurements. We study Wosret in order to constrain its compositional properties and its surface evolution. By comparing them with those of other regions, we aim to identify possible differences among the two lobes of the comet. Methods. We analyzed high-resolution images of the Wosret region acquired between 2015 and 2016 by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) on board the Rosetta spacecraft, at a resolution ranging from 2-10 m/px before and close to perihelion, up to 0.07-0.2 m/px in the post-perihelion images. The OSIRIS images were processed with the OSIRIS standard pipeline, then converted into I/F radiance factors and corrected for the viewing and illumination conditions at each pixel using the Lommel-Seeliger disk function. Spectral slopes were computed in the 535-882 nm range. Results. We observed a few morphological changes in Wosret, related to local dust coating removal with an estimated depth of ∼ 1 m, along with the formation of a cavity measuring 30 m in length and 6.5 m in depth, for a total estimated mass loss of 1.2 × 10 6 kg. The spectrophotometry of the region is typical of medium-red regions of comet 67P, with spectral slope values of 15-16 %/(100 nm) in pre-perihelion data acquired at phase angle 60 o . As observed globally for the comet, also Wosret shows spectral slope variations during the orbit linked to the seasonal cycle of water, with colors getting relatively bluer at perihelion. Wosret has a spectral phase reddening of 0.0546 ×10 −4 nm −1 deg −1 , which is about a factor of 2 lower than what was determined for the nucleus northern hemisphere regions, possibly indicating a reduced surface micro-roughness due to the lack of widespread dust coating. A few tiny bright spots are observed and we estimate a local water-ice enrichment up to 60% in one of them. Morphological features such as "goosebumps" or clods are widely present and larger in size than similar features located in the big lobe. Conclusions. Compared to Anhur and Khonsu, two southern hemisphere regions in the big lobe which have been observed under similar conditions and also exposed to high insolation during perihelion, Wosret exhibits fewer exposed volatiles and less morphological variations due to activity events. Considering that the high erosion rate in Wosret unveils part of the inner layers of the small lobe, our analysis indicates that the small lobe has different physical and mechanical properties than the big one and a lower volatile content, at least in its uppermost layers. These results support the hypothesis that comet 67P originated from the merging of two distinct bodies in the early Solar System.

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“…A linear phase function coefficient of 0.03 mag deg −1 is further assumed. For the nucleus, we also assumed p V =0.07, and the same density (ρ N ) as for the particles (i.e., ρ N =ρ d ), but a steeper linear phase coefficient of 0.047 mag deg −1 , based on the precise estimates for the nucleus of comet 67P from Rosetta/OSIRIS measurements (Fornasier et al 2015).…”

Section: Dust Tail Modelingmentioning

confidence: 99%

The activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with the 10.4m GTC.

Licandro¹,

León²,

Moreno

et al. 2024

Preprint

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Context. The existence of comets with heliocentric orbital periods close to that of Jupiter (i.e., co-orbitals) has been known for some time. Comet 295P/LINEAR (2002 AR 2 ) is a well-known quasi-satellite of Jupiter. However, their orbits are not long-term stable, and they may eventually experience flybys with Jupiter at very close range, close enough to trigger tidal disruptions like the one suffered by comet Shoemaker-Levy 9 in 1992. Aims. Our aim was to study the observed activity and the dynamical evolution of the Jupiter transient co-orbital comet P/2019 LD 2 (ATLAS) and its dynamical evolution. Methods. We present results of an observational study of P/2019 LD 2 carried out with the 10.4 m Gran Telescopio Canarias (GTC) that includes image analyses using a Monte Carlo dust tail fitting code to characterize its level of cometary activity, and spectroscopic studies to search for gas emission. We also present N-body simulations to explore its past, present, and future orbital evolution. Results. Images of P/2019 LD 2 obtained on 2020 May 16, show a conspicuous coma and tail, but the spectrum obtained on 2020 May 17, does not exhibit any evidence of CN, C 2 , or C 3 emission. The comet brightness in a 2.6 aperture diameter is r = 19.34±0.02 mag, with colors (g − r ) = 0.78 ± 0.03, (r − i ) = 0.31 ± 0.03, and (i − z ) = 0.26 ± 0.03. The temporal dependence of the dust loss rate of P/2019 LD 2 can be parameterized by a Gaussian function having a full width at half maximum of 350 days, with a maximum dust mass loss rate of 60 kg s −1 reached on 2019 August 15. The total dust loss rate from the beginning of activity until the GTC observation date (2020 May 16) is estimated at 1.9×10 9 kg. Comet P/2019 LD 2 is now an ephemeral co-orbital of Jupiter, following what looks like a short arc of a quasi-satellite cycle that started in 2017 and will end in 2028. On 2063 January 23, it will experience a very close encounter with Jupiter at perhaps 0.016 au; its probability of escaping the solar system during the next 0.5 Myr is estimated to be 0.53±0.03. Conclusions. Photometry and tail model results show that P/2019 LD 2 is a kilometer-sized object, in the size range of the Jupiterfamily comets, with a typical comet-like activity most likely linked to sublimation of crystalline water ice and clathrates. Its origin is still an open question. Our numerical studies give a probability of this comet having been captured from interstellar space during the last 0.5 Myr of 0.49±0.02 (average and standard deviation), 0.67±0.06 during the last 1 Myr, 0.83±0.06 over 3 Myr, and 0.91±0.09 during the last 5 Myr.

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Phase reddening on asteroid Bennu from visible and near-infrared spectroscopy

Cited by 29 publications

References 75 publications

Weak spectral features on (101995) Bennu from the OSIRIS-REx Visible and InfraRed Spectrometer

Weak spectral features on (101995) Bennu from the OSIRIS-REx Visible and InfraRed Spectrometer

Small lobe of comet 67P: Characterization of the Wosret region with ROSETTA-OSIRIS

The activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with the 10.4m GTC.

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