A spectroscopic study of the Themis family

Florczak, M.; Lazzaro, D.; Mothé-Diniz, T.; Angeli, Cláudia A.; Betzler, Alberto Silva

doi:10.1051/aas:1999150

Cited by 47 publications

(52 citation statements)

References 23 publications

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“…These data suggest the Beagle family is dominated by B-type asteroids, which are characterized by negatively sloped (blue) spectra (Tholen 1984;Bus & Binzel 2002a). The Themis asteroids show a range of C, B, F and G spectral types (Tholen 1984), consistent with the observations of other Themis members (Florczak et al 1999). …”

Section: Resultssupporting

confidence: 80%

“…Therefore, the low fraction of features in the Beagle asteroids likely reflects an intrinsically low phyllosilicate content. However, considering the higher fraction (35-60%) of large Themis members with phyllosilicate features (Florczak et al 1999), we postulate the diagnostic features have been removed due to regolith evolution and space weathering processes. We describe this hypothesis further in § 5.2.…”

Section: C-complex Space Weathering Trendsmentioning

confidence: 89%

“…However, follow-up observations are needed to assess whether these trends can be reproduced. Florczak et al (1999) and Fornasier et al (2014) suggest that the 0.7 µm feature is less frequent among asteroids with decreasing diameters. Data from the SMASS II survey show a high fraction of hydrated members in the young (Nesvorný et al 2003, 8.3 Myr;) Veritas asteroid family (Bus & Binzel 2002b), so we took spectra of 5 randomly selected small (D < 10 km) and 2 moderately sized (D∼20 km) Veritas members to test if the 0.7 µm feature was observable on small diameter objects.…”

Section: Spectral Slopesmentioning

confidence: 99%

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Space weathering trends among carbonaceous asteroids

Kaluna

Masiero

Meech

2016

Icarus

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We present visible spectroscopic and albedo data of the 2.3 Gyr old Themis family and the <10 Myr old Beagle sub-family. The slope and albedo variations between these two families indicate C-complex asteroids become redder and darker in response to space weathering. Our observations of Themis family members confirm previously observed trends where phyllosilicate absorption features are less common among small diameter objects. Similar trends in the albedos of large (>15 km) and small (≤15 km) Themis members suggest these phyllosilicate feature and albedo trends result from regolith variations as a function of diameter. Observations of the Beagle asteroids show a small, but notable fraction of members with phyllosilicate features. The presence of phyllosilicates and the dynamical association of the main-belt comet 133P/Elst-Pizarro with the Beagle family imply the Beagle parent body was a heterogenous mixture of ice and aqueously altered minerals.Subject headings: main belt asteroids, carbonaceous asteroids, space weathering

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Section: Resultssupporting

confidence: 80%

Section: C-complex Space Weathering Trendsmentioning

confidence: 89%

Section: Spectral Slopesmentioning

confidence: 99%

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Space weathering trends among carbonaceous asteroids

Kaluna

Masiero

Meech

2016

Icarus

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“…Given their origin from a common parent, Themis family members are thought to be compositionally homogeneous, as corroborated by observational studies showing that the family is dominated by primitive C-type asteroids that also exhibit signs of aqueous alteration (Bell 1989;Florczak et al 1999;Ivezić et al 2002;Mothé-Diniz et al 2005). The family is also characterized by a high rate of collisions relative to the general main-belt population (Farinella & Davis 1992;Dell'Oro et al 2001).…”

Section: Survey Designmentioning

confidence: 94%

The Hawaii trails project: comet-hunting in the main asteroid belt

Hsieh

2009

A&A

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Context. The mysterious solar system object 133P/(7968) Elst-Pizarro is dynamically asteroidal, yet displays recurrent comet-like dust emission. Two scenarios were hypothesized to explain this unusual behavior: 1) 133P is a classical comet from the outer solar system that has evolved onto a main-belt orbit or 2) 133P is a dynamically ordinary main-belt asteroid on which subsurface ice has recently been exposed. If 1) is correct, the expected rarity of a dynamical transition onto an asteroidal orbit implies that 133P could be alone in the main belt. In contrast, if 2) is correct, other icy main-belt objects should exist and could also exhibit cometary activity. Aims. Believing 133P to be a dynamically ordinary, yet icy main-belt asteroid, I set out to test the primary prediction of the hypothesis: that 133P-like objects should be common and could be found by an appropriately designed observational survey. Methods. I conducted just such a survey -the Hawaii Trails Project -of selected main-belt asteroids in a search for objects displaying cometary activity. Optical observations were made of targets selected from among the Themis, Koronis, and Veritas asteroid families, the Karin asteroid cluster, and low-inclination, kilometer-scale outer-belt asteroids, using the Lulin 1.0 m, small and moderate aperture research telescope system (SMARTS) 1.0 m, University of Hawaii 2.2 m, southern astrophysical research (SOAR) 4.1 m, Gemini North 8.1 m, Subaru 8.2 m, and Keck I 10 m telescopes. Results. I made 657 observations of 599 asteroids, discovering one active object now known as 176P/LINEAR, leading to the identification of the new cometary class of main-belt comets (MBCs). These results suggest that there could be ∼100 currently active MBCs among low-inclination, kilometer-scale outer-belt asteroids. Physically and statistically, MBC activity is consistent with initiation by meter-sized impactors. The estimated rate of impacts and sizes of resulting active sites, however, imply that 133P-sized bodies should become significantly devolatilized over Gyr timescales, suggesting that 133P, and possibly the other MBCs as well, could be secondary, or even multigenerational, fragments from recent breakup events.

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“…6.1, may mean that the sublimation strength at the time was several orders of magnitude weaker than might be expected for Themis closer to perihelion. Many members of the Themis family show evidence for hydration (Florczak et al 1999;Takir and Emery 2012), and the second largest member of the family after Themis itself-(90) Antiope-might have some surface water ice (Hargrove et al 2015).…”

Section: Evidence For Water In Asteroidsmentioning

confidence: 99%

The Main Belt Comets and ice in the Solar System

Snodgrass

Agarwal

Combi

et al. 2017

Astron Astrophys Rev

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We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies.

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A spectroscopic study of the Themis family

Cited by 47 publications

References 23 publications

Space weathering trends among carbonaceous asteroids

Space weathering trends among carbonaceous asteroids

The Hawaii trails project: comet-hunting in the main asteroid belt

The Main Belt Comets and ice in the Solar System

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