Formation of Iapetus’ Extreme Albedo Dichotomy by Exogenically Triggered Thermal Ice Migration

Spencer, J. R.; Denk, T.

doi:10.1126/science.1177132

Cited by 80 publications

(91 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The origin of the material that causes the albedo dichotomy of Iapetus has been the subject of a long standing debate (Buratti and Hicks, 2003;Spencer and Denk, 2010;Tosi et al, 2010). However, Clark et al (2008Clark et al ( , 2011b, showed that the visible colors and UV absorber are consistent with a single source with varying abundance of the contaminants.…”

Section: Introduction and Rationalementioning

confidence: 99%

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Ciarniello

Capaccioni

Filacchione

et al. 2011

Icarus

View full text Add to dashboard Cite

The surface properties of the icy bodies in the saturnian system have been investigated by means of the CASSINI-VIMS (Visual Infrared Mapping Spectrometer) hyperspectral imager which operates in the 0.35-5.1 m wavelength range. In particular, we have analyzed 111 full disk hyperspectral images of Rhea ranging in solar phase between 0.08° and 109.8°. These data have been previously analyzed by Filacchione et al. (2007Filacchione et al. ( , 2010 to study, adopting various "spectral indicators" (such as spectral slopes, band depth, continuum level, etc.), the relations among various saturnian satellites.As a further step we proceed in this paper to a quantitative evaluation of the physical parameters determining the spectrophotometric properties of Rhea's surface. To do this we have applied Hapke (1993) IMSA model (Isotropic Multiple Scattering Approximation) which allow us to model the phase function at VIS-IR (visible-infrared) wavelengths as well as the spectra taking into account various types of mixtures of surface materials. Thanks to this method we have been able to constrain the size of water ice particles covering the surface, the amount of organic contaminants, the large scale surface roughness and the opposition effect surge. From our analysis it appears that wavelength dependent parameters, e.g. opposition surge width (h) and single-particle phase function parameters (b,v), are strongly correlated to the estimated single-scattering albedo of particles. For Rhea the best fit solution is obtained by assuming:1) an intraparticle mixture of crystalline water ice and a small amount (0.4%) of Triton tholin; 2) a monodisperse grain size distribution having a particle diameter a m = 38 µm; and 3) a surface roughness parameter value of 33°. The study of phase function shows that both Shadow Hiding and Coherent Backscattering contribute to the opposition surge. This study represents the first attempt, in the case of Rhea, to join the spectral and the photometric analysis. The surface model we derived gives a good quantitative description of both spectrum and phase curve of the satellite. The same approach and model, with appropriate modifications, shall be applied to VIMS data of the other icy satellites of Saturn, in order to reveal similarities and differences in the surface characteristics to understand how these bodies interact with their environment.

show abstract

Section: Introduction and Rationalementioning

confidence: 99%

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Ciarniello

Capaccioni

Filacchione

et al. 2011

Icarus

View full text Add to dashboard Cite

show abstract

“…The albedo value of Iapetus' leading side (∼0.04) reported by Spencer & Denk (2010) is in the range of the typical albedo values of F-type asteroids, i.e., 0.03-0.07 (Tedesco et al 2002). However, the polarization minimum of Iapetus' leading side is slightly shallower than the typical value for low-albedo asteroids, which is ∼−1.6%, and slightly deeper than that of the F-type asteroid 419 Aurelia, which is ∼1.0% (Belskaya et al 2005).…”

Section: Discussionmentioning

confidence: 93%

Polarization of Saturn’s moon Iapetus

Ejeta

Muinonen

Boehnhardt

et al. 2013

A&A

View full text Add to dashboard Cite

Context. The surface properties of atmosphereless solar system objects can be constrained by investigating the nature of the polarized light scattered from their surfaces. Aims. We provide new and precise measurements of the phase angle and the wavelength dependence of linear polarization on the leading side of Iapetus over the maximum phase angle range accessible from Earth (∼0.5−6.0• ) and over a broad spectral range (400-800 nm), thereby identifying the polarimetric characteristics of its dark material. Moreover, we provide circular spectral polarization measurement of the same side of Iapetus at one phase angle, which was performed aiming at detection of chiral signatures on its surface. We also compare our new polarization measurements with those of the trailing hemisphere of Iapetus which were obtained in our previous work. Methods. Using the FORS2 instrument of the ESO VLT, we performed spectro-polarimetric observations of Iapetus' leading side. Results. While the linear polarization measurements of Iapetus' leading side show an opposite trend in phase angle dependence to that of its trailing hemisphere, the polarization values measured for the two hemispheres around similar phase angles (in the range ∼3.0−6.0• ) differ by a factor of three. Besides this, the degree of negative linear polarization of Iapetus' leading hemisphere shows a slight dependence on the wavelengths of observations. Furthermore, like that of its trailing hemisphere, the circular polarization measurement of Iapetus' leading side indicates no evidence of a significant amount of optically active (chiral) molecules on its surface.

show abstract

“…A thermal model of the evolution of Iapetus' surface (Spencer & Denk 2010), in which H 2 O ice is mobilized by the higher temperatures in the dark hemisphere and re-condensed elsewhere, convincingly reproduces the albedo pattern seen today. An absorption band at 3.28 μm, attributed to polycyclic aromatic hydrocarbons, has been identified in the low-albedo material on Iapetus (Cruikshank et al 2008).…”

Section: Polycyclic Aromatic and Aliphatic Hydrocarbons On Saturn's Smentioning

confidence: 87%

Organic materials in planetary and protoplanetary systems: nature or nurture?

Ore

Fulchignoni

Cruikshank

et al. 2011

A&A

View full text Add to dashboard Cite

Aims. The objective of this work is to summarize the discussion of a workshop aimed at investigating the properties, origins, and evolution of the materials that are responsible for the red coloration of the small objects in the outer parts of the solar system. Because of limitations or inconsistencies in the observations and, until recently, the limited availability of laboratory data, there are still many questions on the subject. Our goal is to approach two of the main questions in a systematic way: -Is coloring an original signature of materials that are presolar in origin ("nature") or stems from post-formational chemical alteration, or weathering ("nurture")? -What is the chemical signature of the material that causes spectra to be sloped towards the red in the visible? We examine evidence available both from the laboratory and from observations sampling different parts of the solar system and circumstellar regions (disks). Methods. We present a compilation of brief summaries gathered during the workshop and describe the evidence towards a primordial vs. evolutionary origin for the material that reddens the small objects in the outer parts of our, as well as in other, planetary systems. We proceed by first summarizing laboratory results followed by observational data collected at various distances from the Sun. Results. While laboratory experiments show clear evidence of irradiation effects, particularly from ion bombardment, the first obstacle often resides in the ability to unequivocally identify the organic material in the observations. The lack of extended spectral data of good quality and resolution is at the base of this problem. Furthermore, that both mechanisms, weathering and presolar, act on the icy materials in a spectroscopically indistinguishable way makes our goal of defining the impact of each mechanism challenging. Conclusions. Through a review of some of the workshop presentations and discussions, encompassing laboratory experiments as well as observational data, we infer that both "nature" and "nurture" are instrumental in the coloration of small objects in the outer parts Article published by EDP Sciences A98, page 1 of 14 A&A 533, A98 (2011) of the solar system. While in the case of some observations it is clear that the organic reddening material originated before the solar nebula (i.e. presolar grains found in meteorites), for many other cases pointers are not as clear and indicate a concurrence of both processes.

show abstract

Formation of Iapetus’ Extreme Albedo Dichotomy by Exogenically Triggered Thermal Ice Migration

Cited by 80 publications

References 36 publications

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Hapke modeling of Rhea surface properties through Cassini-VIMS spectra

Polarization of Saturn’s moon Iapetus

Organic materials in planetary and protoplanetary systems: nature or nurture?

Contact Info

Product

Resources

About