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Origins of colors variability among C-cluster main-belt asteroids

Abstract : The Sloan Digital Sky Survey provides colors for more than 100,000 moving objects, among which a significant fraction has albedos determined. Here we combined colors and albedo in order to perform a cluster analysis on the main-belt asteroid population, and identify a C-cluster, a group of asteroid related to C-type as defined in earlier work. Members of this C-cluster are in fair agreement with the color boundaries of B and C-type defined in DeMeo and Carry (2013). We then compare colors of C-cluster asteroids to those of carbonaceous chondrites powders, while taking into account the effect of phase angle. We show that only CM chondrites have colors in the range of C-cluster asteroids, CO, CR and CV chondrites being significantly redder. Also, CM chondrites powders are on average slightly redder than the average C-cluster. The colors of C-cluster members are further investigated by looking at color variations as a function of asteroid diameter. We observe that the visible slope becomes bluer with decreasing asteroids diameter, and a transition seems to be present around 20 km. We discuss the origin of this variation and, if not related to a bias in the dataset - analysis, we conclude that it is related to the surface texture of the objects, smaller objects being covered by rocks or large fragments, while larger objects are covered by a particulate surface. The blueing is interpreted by an increased contribution of the first reflection in the case of rock-dominated surfaces, which can scatter light in a Rayleigh-like manner. We do not have unambiguous evidence of space weathering within the C-cluster based on this analysis, however the generally bluer nature of C-cluster objects compared to CM chondrites could be to some extent related to space weathering.
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Submitted on : Monday, June 27, 2022 - 8:50:32 AM
Last modification on : Wednesday, June 29, 2022 - 3:09:35 AM

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Pierre Beck, Olivier Poch. Origins of colors variability among C-cluster main-belt asteroids. Icarus, 2021, 365, ⟨10.1016/j.icarus.2021.114494⟩. ⟨insu-03705278⟩

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