Collisions, cosmic radiation and the colors of the Trojan asteroids

Melita, M. D.; Strazzulla, G.; Bar‐Nun, A.

doi:10.1016/j.icarus.2009.04.024

Cited by 12 publications

(15 citation statements)

References 36 publications

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“…In particular, the color bimodality has no current explanation. Although some theories have been forwarded to produce the range of Trojan colors through ongoing processes such as surface gardening and/or various irradiation mechanisms (e.g., Melita et al 2009), none of these theories predicts a bimodality in color, instead yielding a single broad color distribution that is inconsistent with observations. On the basis of the differing spectral properties of LR and R Trojans, Emery et al (2011) suggested that perhaps one of the two sub-populations formed in the Main Belt asteroid region, while the other formed in the outer solar system before being captured by Jupiter.…”

Section: Introductionmentioning

confidence: 99%

A Hypothesis for the Color Bimodality of Jupiter Trojans

Wong

Brown

2016

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One of the most enigmatic and hitherto unexplained properties of Jupiter Trojans is their bimodal color distribution. This bimodality is indicative of two sub-populations within the Trojans, which have distinct size distributions. In this paper, we present a simple, plausible hypothesis for the origin and evolution of the two Trojan color sub-populations. In the framework of dynamical instability models of early solar system evolution, which suggest a common primordial progenitor population for both Trojans and Kuiper Belt objects, we use observational constraints to assert that the color bimodalities evident in both minor body populations developed within the primordial population prior to the onset of instability. We show that, beginning with an initial composition of rock and ices, location-dependent volatile loss through sublimation in this primordial population could have led to sharp changes in the surface composition with heliocentric distance. We propose that the depletion or retention of H 2 S ice on the surface of these objects was the key factor in creating an initial color bimodality. Objects that retained H 2 S on their surfaces developed characteristically redder colors upon irradiation than those that did not. After the bodies from the primordial population were scattered and emplaced into their current positions, they preserved this primordial color bimodality to the present day. We explore predictions of the volatile loss model-in particular, the effect of collisions within the Trojan population on the size distributions of the two sub-populations-and propose further experimental and observational tests of our hypothesis.

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Section: Introductionmentioning

confidence: 99%

A Hypothesis for the Color Bimodality of Jupiter Trojans

Wong

Brown

2016

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“…However, since the incident radiation flux on the surface of a spherical body scales in tandem with size, this flattening effect is expected to be the same across the full range of Trojan sizes and hence does not explain the discrepant faint-end slopes observed in the magnitude distributions of the color populations. Furthermore, the timescale for flattening the spectrum of a R Trojan is much smaller than the time that has elapsed since emplacement and formation(Melita et al 2009), so if irradiation is the sole mechanism for converting R objects to LR ones, one would not expect any R objects to remain. InMelita et al (2009), an additional mechanism is proposed whereby minor cratering events disrupt the spectrally flattened irradiation crust and excavate underlying material, which the authors of that work posit as being red in color, consistent with that of typical surfaces rich in complex organic materials.…”

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confidence: 99%

The Differing Magnitude Distributions of the Two Jupiter Trojan Color Populations

2014

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The Jupiter Trojans are a significant population of minor bodies in the middle Solar System that have garnered substantial interest in recent years. Several spectroscopic studies of these objects have revealed notable bimodalities with respect to near-infrared spectra, infrared albedo, and color, which suggest the existence of two distinct groups among the Trojan population. In this paper, we analyze the magnitude distributions of these two groups, which we refer to as the red and less red color populations. By compiling spectral and photometric data from several previous works, we show that the observed bimodalities are self-consistent and categorize 221 of the 842 Trojans with absolute magnitudes in the range H < 12.3 into the two color populations. We demonstrate that the magnitude distributions of the two color populations are distinct to a high confidence level (> 95%) and fit them individually to a broken power law, with special attention given to evaluating and correcting for incompleteness in the Trojan catalog as well as incompleteness in our categorization of objects. A comparison of the best-fit curves shows that the faint-end power-law slopes are markedly different for the two color populations, which indicates that the red and less red Trojans likely formed in different locations. We propose a few hypotheses for the origin and evolution of the Trojan population based on the analyzed data.

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“…compatible with the age of the surfaces of the small objects in the outer Solar System (e.g. Brunetto et al 2006;Melita et al 2009). …”

Section: Colorsmentioning

confidence: 89%

“…and evaporation processes (see e.g., Doressoundiram et al 2002;Peixinho et al 2004;Melita et al 2009;Grundy 2009).…”

Section: Colorsmentioning

confidence: 99%

Ion irradiation induced effects on airless bodies in the Solar System

Strazzulla

2012

EAS Publications Series

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Abstract. Irradiation by cosmic ions plays a relevant role in the "space weathering" of solid materials in the airless bodies (rocky and/or icy objects) in the Solar System. Here, I discuss about some of the effects that have been studied in "simulation" experiments with a view to their astrophysical relevance. In particular I review some experimental results obtained so far after irradiation of relevant materials, namely: sputtering, ion implantation, and chemical synthesis of molecular species different from the original ones. All of those effects are accomplished by changes in the optical properties of irradiated layers and then of the color of the surfaces of the airless bodies. Some specific examples of the application of the experimental results to the physics and chemistry of planetary surfaces are discussed as well.

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Collisions, cosmic radiation and the colors of the Trojan asteroids

Cited by 12 publications

References 36 publications

A Hypothesis for the Color Bimodality of Jupiter Trojans

A Hypothesis for the Color Bimodality of Jupiter Trojans

The Differing Magnitude Distributions of the Two Jupiter Trojan Color Populations

Ion irradiation induced effects on airless bodies in the Solar System

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