Compositional Evolution of Saturn's Rings Due to Meteoroid Bombardment

Cuzzi, Jeffrey N.; Estrada, P. R.

doi:10.1006/icar.1997.5863

Cited by 159 publications

(193 citation statements)

References 77 publications

(7 reference statements)

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“…Substituting the debris size distribution x k ðiÞ ∼ i=k α into the basic kinetic equations [2], we note that the equation for the monomer production rate coincides with Eq. 4, up to a factor in the coefficients A ij .…”

Section: [4]mentioning

confidence: 99%

“…4, up to a factor in the coefficients A ij . At the same time, the general equations [2] for n k have the same terms as Eq. 3 for complete decomposition, but with two extra terms-the fourth and fifth terms in Eq.…”

Section: [4]mentioning

confidence: 99%

“…Moreover, it may be shown analytically (SI Text) that the form [15] of the distribution persists when collisions with erosion are involved. We checked this conclusion numerically, solving the kinetic equations [2] with a power-law, exponential size distribution of debris and for collisions with an erosion (Fig. 2).…”

Section: [4]mentioning

confidence: 99%

“…B ombardment of Saturn's rings by interplanetary meteoroids (1)(2)(3) and the observation of rapid processes in the ring system (4) indicate that the shape of the particle size distribution is likely not primordial or a direct result of the ring-creating event. Rather, ring particles are believed to be involved in active accretion-destruction dynamics (5-13) and their sizes vary over a few orders of magnitude as a power law (14)(15)(16)(17), with a sharp cutoff for large sizes (18)(19)(20)(21).…”

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Size distribution of particles in Saturn’s rings from aggregation and fragmentation

Brilliantov

Krapivsky

Bodrova

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

131

129

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Saturn's rings consist of a huge number of water ice particles, with a tiny addition of rocky material. They form a flat disk, as the result of an interplay of angular momentum conservation and the steady loss of energy in dissipative interparticle collisions. For particles in the size range from a few centimeters to a few meters, a power-law distribution of radii, ∼ r −q with q ≈ 3, has been inferred; for larger sizes, the distribution has a steep cutoff. It has been suggested that this size distribution may arise from a balance between aggregation and fragmentation of ring particles, yet neither the power-law dependence nor the upper size cutoff have been established on theoretical grounds. Here we propose a model for the particle size distribution that quantitatively explains the observations. In accordance with data, our model predicts the exponent q to be constrained to the interval 2.75 ≤ q ≤ 3.5. Also an exponential cutoff for larger particle sizes establishes naturally with the cutoff radius being set by the relative frequency of aggregating and disruptive collisions. This cutoff is much smaller than the typical scale of microstructures seen in Saturn's rings. (1-3) and the observation of rapid processes in the ring system (4) indicate that the shape of the particle size distribution is likely not primordial or a direct result of the ring-creating event. Rather, ring particles are believed to be involved in active accretion-destruction dynamics (5-13) and their sizes vary over a few orders of magnitude as a power law (14-17), with a sharp cutoff for large sizes (18-21). Moreover, tidal forces fail to explain the abrupt decay of the size distribution for house-sized particles (22). One wishes to understand the following: (i) Can the interplay between aggregation and fragmentation lead to the observed size distribution? And (ii) is this distribution peculiar for Saturn's rings, or is it universal for planetary rings in general? To answer these questions quantitatively, one needs to elaborate a detailed model of the kinetic processes in which the ring particles are involved. Here we develop a theory that quantitatively explains the observed properties of the particle size distribution and show that these properties are generic for a steady state, when a balance between aggregation and fragmentation holds. Our model is based on the hypothesis that collisions are binary and that they may be classified as aggregative, restitutive, or disruptive (including collisions with erosion); which type of collision is realized depends on the relative speed of colliding particles and their masses. We apply the kinetic theory of granular gases (23, 24) for the multicomponent system of ring particles to quantify the collision rate and the type of collision. Results and DiscussionModel. Ring particles may be treated as aggregates built up of primary grains (9) of a certain size r 1 and mass m 1 . [Observations indicate that particles below a certain radius are absent in dense rings (16).] Denote by m k = km 1 the mass of rin...

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Section: [4]mentioning

confidence: 99%

Section: [4]mentioning

confidence: 99%

Section: [4]mentioning

confidence: 99%

mentioning

confidence: 99%

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Size distribution of particles in Saturn’s rings from aggregation and fragmentation

Brilliantov

Krapivsky

Bodrova

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

131

129

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“…The best-fitting models described in Table 3 are intimate (salt and pepper-like) mixtures that include some molecular or intra-mixtures of tholins and ice where the refractive index is calculated by means of the "effective medium" approximation (Bohren & Huffman 1983;Wilson et al 1994;Cuzzi & Estrada 1998). Molecular mixing has its main effect on the visible part of the spectrum, which explains the need for more (triton) tholin in the mixtures along with the fraction contributing in the molecularly mixed part.…”

Section: Modellingmentioning

confidence: 99%

(50000) Quaoar: Surface composition variability

Barucci

Ore

Perna

et al. 2015

A&A

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Aims. The goal of this work is to investigate the composition of the surface of (50000) Quaoar and its spatial variability. Methods. We present new continuous spectra from the visible to near-IR (0.3−2.3 μm) obtained with the X-Shooter instrument at the VLT-ESO at four different epochs on the surface of Quaoar. The data represent the highest spectral resolution data ever obtained for this object and the first near-IR dataset acquired in a single exposure over the entire wavelength range. They are complemented by previously published photometric observations obtained in the near-IR (3.6, 4.5 μm) with the Spitzer Space Telescope, which provide an extra set of constraints in the model calculation. Spectral modelling was performed for the entire wavelength range by means of a code based on the Shkuratov radiative transfer formulation and of an updated value of albedo obtained from recent Herschel observations. Results. We obtained compositional information for different observed areas that can cover about 40% of the assumed rotational period of 8.84 h. Our analysis helps to prove the presence of CH 4 and C 2 H 6 , as previously reported, along with indications of the possible presence of NH 3 ·H 2 O. New evidence of N 2 is inferred from the shift in the CH 4 bands. The albedo at the two Spitzer bands suggests there may be CO diluted in N 2 , and CO 2 for one of the surface locations. Conclusions. The spectral similarities indicate the overall homogeneity of the surface composition of one hemisphere of Quaoar, while some subtle variations are apparent when modelling. The presence of NH 3 ·H 2 O would support the idea that Quaoar's surface may be relatively young.

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