National Workshop on Pluto and the Kuiper Belt 2007

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On January 11-12, 2007, CNES and I organised a National workshop on Pluto and the Kuiper Belt at University of Nantes, one year after the launch of NASA's New Horizons New Horizons spacecraft to Pluto and the Kuiper belt objects farther in the Solar System. Below is the programme of this workshop, the abstracts of presentaitons, and links to the talks that were presented at that time.
New Horizons arrived at Pluto on July 14th, 2015, found new moons: Nix, Hydra, Kerberos and Styx , then discovered and made a flyby of 486958 Arrokoth on January 1st, 2019.

Workshop Program

Pluto and the KBOs: State of our knowledge and their internal and external structures

Pluto and the dwarf planets
William Grundy

This talk will survey discoveries and developments concerning Pluto and the other dwarf planets during the past year since the IAU General Assembly in Prague. The main topics will include: (1) The changing definition of a planet and the dwarf planets. (2) Pluto and Charon. (3) Eris (2003 UB313, a.k.a. Xena). (4) Ceres, the largest object in the asteroid belt. (5) Other possible dwarf planets such as 2003 EL61 (a.k.a. Santa) and Makemake (2005 FY9, a.k.a. Easterbunny).

Ceres in the context of icy solar system bodies
Lucille Le Corre

Pluto, Charon, Triton, Iapetus and Ceres have in common the fact that their mean densities are too high to permit pure water ice composition. The abundances of volatiles, and especially of water ice, varies considerably between these objects, possibly related to the different environments in which they formed. Near-infrared spectroscopy observations of these five bodies are presented and discussed. Ceres, as the largest object of the Main Belt of asteroids, was most likely located inside the "snow line" (inside 2.7 AU), whereas it is thought that Pluto and Charon formed in the trans-Neptunian region. Recent results are shown and comparisons are made with the other icy objects. These spectroscopic observations help to better understand Ceres' surface composition, the mineralogy, the chemical and thermal evolution and, more generally, they give an idea of what to expect for future observations by the Dawn spacecraft which will explore Ceres in 2015.

Physical characterization of transneptunian objects and Centaurs: Color, spectroscopy, and taxonomy
Alain Doressoundiram

The diversity shown by the Kuiper Belt is impressive. However, we can attempt to bring some order if we use both dynamical and physical arguments. The Centaurs and Transneptunian objects (TNOs) have been studied at optical, near and mid-infrared wavelengths using ground-based and space-borne facilities such as the ESO NTT and VLT, the Subaru telescope, the Hubble Space Telescope or the Spitzer Space Telescope. Photometric observations have revealed a great diversity among the trans-Neptunian population. Spectroscopic observations confirm this color diversity and show several objects that exhibit ice absorption features. These features reveal differences in the nature and abundance of volatiles. With the lack of high resolution spectra for most of the objects in our sample, multicolor photometry is used to further constraint the composition of the object surface. These data can give some clues of the origin of colors among TNOs and Centaurs and allow a tentative classification of the populations. Recent results are presented and discussed here in terms of composition, surface properties and taxonomy.

The Keck Adaptive Optics survey of TNOs
Franck Marchis

We have conducted a study of Trans-Neptunian objects (TNOs) using the Keck II telescope and its Adaptive Optics system, starting in 2002. Based on the detection of satellites and estimations of their size, densities of several TNOs have been derived. In a second part of our study, we collected size measurements of 40 TNOs, large enough to have a bulk density similar to the mean density of most satellites, allowing thus meaningful discussion of the thermal and collisional histories of these objects. Recently, we extended this work with the study of binary asteroids, especially TNOs and Trojan binaries. Based on their sizes and orbits, we estimated their mutual-orbit with accurate estimation. We will show how all these results can help to draw a more complete picture of the history and origin of the "third zone" of our solar system.

Constraints on Pluto's volatile distribution and evolution from the study of Jupiter, Saturn, Uranus and Neptune
Olivier Mousis

Constraints on the distribution and evolution of volatiles in Pluto and other big TNOs are given from comparison with the composition of the atmospheres of Jupiter, Saturn, Uranus and Neptune. The current composition of the giant planets in volatiles can be explained if they have trapped significant amounts of heavy elements from the surrounding nebula via the formation of crystalline water ice, in addition to the building block component. This mechanism would have been also at work during the formation of big TNOs like Pluto.

Atmospheric photochemistry of Pluto, general processes and comparison with Triton
Philippe Rousselot

We describe the main photochemical processes at work in Pluto's atmosphere and briefly review the corresponding observations of Pluto, as well as Triton. We also discuss possible similarities and differences between the two objects, including an update on recent Pluto stellar occultations (June 2006).

The geology of Pluto as revealed by New Horizons: Geological forecast at C/A
Daniel Mège

This talk focuses on (1) the possible cryovolcanic activity of Pluto, and (2) the structural geology methods that can be used to infer the thickness of Pluto's brittle "crust" from observations that can be made using LORRI and RALPH onboard New Horizons. Cryovolcanism: Detailed analysis of cryovolcanic activity of Triton shows an amazing diversity of morphologies, which requires ice magmas of various composition, viscosity, and modes of emplacement. Such a diversity may also be observed on Pluto. Tectonics and rheology: The brittle ice shell thickness of Pluto may be constrained from application of fault scaling relationships. Changes in the exponent of the power-law distribution of fault lengths, which can be obtained from imagery, may be indicative of major rheological transitions. By measuring fault length and displacement using imagery and derived digital elevation models, displacement-length-height scaling may help constrain the maximum fault height, i.e. the maximum depth of faulting in the brittle shell, constraining its thickness.

Dynamics of TNOs and the young solar system

Origin of the orbital structure of the Kuiper Belt: New model and open problems
Alessandro Morbidelli

This talk will focus on the characteristics of the Kuiper belt that cannot be explained by its evolution in the framework of the current solar system. I'll review models of primordial solar system evolution that have been proposed to reproduce the Kuiper belt features, outlining advantages and problems of each of them.

Coupling dynamical and collisional evolution of the Kuiper Belt, the Scattered Disk, and the Oort Cloud
Sébastien Charnoz, Alessandro Morbidelli

The Kuiper Belt, the Scattered Disk and the Oort Cloud are dynamically distinct populations of small bodies evolving in the outer regions of the Solar System. Using a hybrid approach (Charnoz & Morbidelli 2003), we try to couple the primordial collisional and dynamical evolution of these three populations in a self-consistent way. We show that the initial planetesimal size distribution that allows an effective mass depletion of the Kuiper Belt by collisional grinding, would decimate also the population of comet-size bodies that end in the Oort Cloud and in the Scattered Disk. These two reservoirs would therefore be too anemic, by a factor 40 to 100, relative to the estimates achieved from the observation of the fluxes of long period and jupiter family comets, respectively. For these two reservoirs to have a sufficient number of comets, the initial size distribution in the planetesimal disk had to be such that the mass depletion by collisional erosion of in the Kuiper belt was negligible.

Orbital and physical characterization of TNO binaries
Daniel Hestroffer

La découverte de corps célestes binaires en attraction gravitationnelle mutuelle est un atout majeur pour connaître leur masse et sonder leur intérieur, deux paramètres fondamentaux difficilement accessibles. Il s'avère que, et c'est une chance, une proportion non négligeable des objets transneptuniens (TNOs) actuellement connus sont des binaires ou systèmes multiples (Noll et al. 2006, DPS#38). Nous présenterons brièvement une méthode de détermination d'orbite de binaires résolues (ou visuelles) spécialement bien adaptée aux cas où l'on ne possède qu'un ensemble restreint de données. Cette méthode d'inversion statistique donne directement la ou le faisceau de solutions, ainsi que les zones de confiances attachées. Nous montrerons quelques exemples pour systèmes de transneptuniens connus. La détermination d'une solution unique est une tâche difficile qui dépend de chacun des systèmes étudiés, mais cependant les données astrométriques obtenues par la caméra HST/HRC montrent que c'est un des instruments le plus adapté à cette problématique...