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At least 55 records · Page 3

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NASA NTRS1989

The interiors of Pluto and Charon - Structure, composition, and implications

Recent models of the internal structure of Pluto and Charon, made possible by analysis of the Pluto/Charon mutual events are reviewed. At a mean density of just over 2 g/cu cm and a predicted rock mass fraction of roughly 0.7, the Pluto/Charon system is significantly rockier than the icy satellites of the giant planets, a contrast which may reflect its formation in a CO-rich outer solar nebula rather than a circumplanetary nebula. Pluto and Charon may in fact be so rocky that they lost volatiles early in their history (possibly during a Charon-forming impact event), although this is still an open issue.

Simonelli, Damon P.↗

NASA NTRS1989

Dynamics of Pluto and Charon

The dynamics of the Pluto-Charon system are reviewed from a historical perspective. Although Pluto's orbit crosses Neptune's, an intricate system of nested resonances keeps these planets apart. Pluto's orbit is apparently chaotic as well. Pluto always keeps the same face turned toward Charon, and vice versa. Tides also damp Charon's orbital eccentricity and inclination. Precession of Pluto's orbital plane causes Pluto's obliquity to vary periodically from formally prograde to retrograde. Pluto is probably an original member of the Solar system, but not an escaped satellite of Neptune.

Dobrovolskis, Anthony R.↗

NASA NTRS1991

Occultations by Pluto and Charon - 1990-1999

The results of a photographic plate search for stars as faint as V = 16 which may be occulted by Pluto or Charon between January 1, 1990 and December 31, 1999 are presented. Circumstances for the closest approach of Pluto to 32 stars and Charon to 28 stars are presented. Photometric information is given for some of the brightest stars found in a search of the Space Telescope Guide Star Catalog for Pluto occultations. Finding charts from Space Telescope Guide Star plates are provided for some of the best events. The brightest star (V = 12.7) may be occulted by both Pluto and Charon on September 26, 1999.

Mink, Douglas J.↗

NASA NTRS1991

Visual and infrared studies of asteroids and the Pluto-Charon system

The strategy of the project was to: (1) analyze light curves of Pluto-Charon mutual eclipse event light curves to derive models of the Pluto-Charon system; (2) use these results in planning and reducing HST observations tentatively scheduled to be obtained in Aug. 1991 to determine Pluto-Charon mass ratio; and (3) obtain visual and IR photometry of selected asteroids to help determine their albedos, sizes, shapes, pole orientations, taxonomic classes, and phase functions.

Tedesco, Edward F.↗

NASA NTRS1997

Charon Toolkit for Parallel, Implicit Structured-Grid Computations: Functional Design

In a previous report the design concepts of Charon were presented. Charon is a toolkit that aids engineers in developing scientific programs for structured-grid applications to be run on MIMD parallel computers. It constitutes an augmentation of the general-purpose MPI-based message-passing layer, and provides the user with a hierarchy of tools for rapid prototyping and validation of parallel programs, and subsequent piecemeal performance tuning. Here we describe the implementation of the domain decomposition tools used for creating data distributions across sets of processors. We also present the hierarchy of parallelization tools that allows smooth translation of legacy code (or a serial design) into a parallel program. Along with the actual tool descriptions, we will present the considerations that led to the particular design choices. Many of these are motivated by the requirement that Charon must be useful within the traditional computational environments of Fortran 77 and C. Only the Fortran 77 syntax will be presented in this report.

VanderWijngaart, Rob F.↗

NASA NTRS2004

Pluto-Charon: Infrared Reflectance from 3.6 to 8.0 Micrometers

We have measured the spectral reflectance of the Pluto-Charon pair at 3.6, 4.5, 5.8, and 8.0 micrometers with the Infrared Array Camera (IRAC) (G. G. Fazzio et al. Ap.J.Supp. 154, 10-17, 2004) on the Spitzer Space Telescope (STS), at eight different longitudes that cover a full rotation of the planet. STS does not have sufficient resolution to separate the light from the planet and the satellite. The image of the Pluto-Charon pair is clearly visible at each of the four wavelengths. We will discuss the spectral reflectance in terms of models that include the known components of Pluto and Charon s surfaces, and evidence for diurnal variations.

Cruikshank, Dale P.↗

NASA NTRS2016

The Geology of Pluto and Charon Through the Eyes of New Horizons

NASA's New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto's encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection, with a crater retention age no greater than approximately 10 million years. Surrounding terrains show active glacial flow, apparent transport and rotation of large buoyant water-ice crustal blocks, and pitting, the latter likely caused by sublimation erosion and/or collapse. More enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic and ridges with complex bladed textures. Pluto also has ancient cratered terrains up to approximately 4 billion years old that are extensionally faulted and extensively mantled and perhaps eroded by glacial or other processes. Charon does not appear to be currently active, but experienced major extensional tectonism and resurfacing (probably cryovolcanic) nearly 4 billion years ago. Impact crater populations on Pluto and Charon are not consistent with the steepest impactor size-frequency distributions proposed for the Kuiper belt.

Moore, Jeffrey M.↗

NASA NTRS2018

The Geology of Pluto and Charon as Revealed by New Horizons

NASA's New Horizons spacecraft has revealed that Pluto and Charon exhibit strikingly different surface appearances, despite their similar densities and presumed bulk compositions. Much of Pluto's surface can be attributed to surface-atmosphere interactions and the mobilization of volatile ices by insolation. Many valley systems appear to be the consequence of glaciation involving nitrogen ice. Other geological activity requires or required internal heating. The convection and advection of volatile ices in Sputnik Planum can be powered by present-day radiogenic heat loss. On the other hand, the prominent mountains at the western margin of Sputnik Planum, and the strange, multi-km-high mound features to the south, probably composed of H2O, are young geologically as inferred by light cratering and superposition relationships. Their origin, and what drove their formation so late in Solar System history, is under investigation. The dynamic remolding of landscapes by volatile transport seen on Pluto is not unambiguously evident on Charon. Charon does, however, display a large resurfaced plain and globally engirdling extensional tectonic network attesting to its early endogenic vigor.

Moore, Jefrey M.↗

NASA NTRS2014

Gemini NorthNIRI Spectra of Pluto and Charon: Simultaneous Analysis of the Surface and Atmosphere

94035We report on our analysis of blended Pluto and Charon spectra over the wavelength range 1.4 to 2.5 m as obtained by the NIRI instrument on Gemini North on June 25-28, 2004. The data have a resolving power () around 1500 and a SNR around 200 per pixel. The observed blended spectra are compared to models that combine absorption from the solid ice on the surface using Hapke theory, and absorption from the gaseous atmosphere. We assume the spectrum is a combination of several spatially separate spectral units: a CH4-rich ice unit, a volatile unit (an intimate mixture of N2, CH4 and CO), and a Charon unit (H2O, ammonia hydrate and kaolinite). We test for the presence of hydrocarbons (i.e. C2H6) and nitriles (i.e. HCN) and examine cases where additional ices are present as either pure separate spatial units, mixed with the CH4-rich unit or part of the volatile unit. We conclude that 2-4 of Plutos surface is covered with pure-C2H6 and our identification of C2H6 is significantly strengthened when absorption due to gaseous CH4 is included. The inclusion of Plutos atmosphere demonstrates that low-resolution, high-SNR observations are capable of detecting Plutos atmosphere during a time when Plutos atmosphere may have been undergoing rapid changes (1988-2002) and no high-resolution spectra were obtained. In particular, we identify features at 1.665 and 2.317 m as the Q-branch of the 23 and 3+4 bands of gaseous CH4, respectively. The later band is also evident in many previously published spectra of Pluto. Our analysis finds it is unnecessary to include 13CO to explain the depth of the 2.405 m, which has been previously suggested to be a spectral blended with C2H6, but we cannot definitively rule out its presence. Funding for this work (Cook) has been provided by a NASA-PATM grant.

Charon↗

NASA NTRS2017

The Geology of Charon as Revealed by New Horizons

Pluto's large moon Charon [radius 606 km; density = 1.70 g cm(exp. -3)] exhibits a striking variety of landscapes. Charon can be divided into two broad provinces separated by a roughly aligned assemblage of ridges and canyons, which span from east to west. North of this tectonic belt is rugged, cratered terrain (Oz Terra); south of it are smoother but geologically complex plains (Vulcan Planum). (All place names here are informal.) Relief exceeding 20 km is seen in limb profiles and stereo topography.

Charon↗

DOE OSTI2020

Charon User Manual (V.2.1) (Rev.01)

This manual gives usage information for the Charon semiconductor device simulator. Charon was developed to meet the modeling needs of Sandia National Laboratories and to improve on the capabilities of the commercial TCAD simulators; in particular, the additional capabilities are running very large simulations on parallel computers and modeling displacement damage and other radiation effects in significant detail. The parallel capabilities are based around the MPI interface which allows the code to be ported to a large number of parallel systems, including linux clusters and proprietary "big iron" systems found at the national laboratories and in large industrial settings.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2022

Charon User Manual: v. 2.2 (revision1)

This manual gives usage information for the Charon semiconductor device simulator. Charon was developed to meet the modeling needs of Sandia National Laboratories and to improve on the capabilities of the commercial TCAD simulators; in particular, the additional capabilities are running very large simulations on parallel computers and modeling displacement damage and other radiation effects in significant detail. The parallel capabilities are based around the MPI interface which allows the code to be ported to a large number of parallel systems, including linux clusters and proprietary “big iron” systems found at the national laboratories and in large industrial settings.

42 ENGINEERING↗

DOE OSTI2020

A Numerical Method for Determining the Elements of Circumbinary Orbits and Its Application to Circumbinary Planets and the Satellites of Pluto-Charon

Planets and satellites orbiting a binary system exist in the solar system and extrasolar planetary systems. Their orbits can be significantly different from Keplerian orbits, if they are close to the binary and the secondary-to-primary mass ratio is high. A proper description of a circumbinary orbit is in terms of the free eccentricity e {sub free} at the epicyclic frequency κ {sub 0}, forced eccentricity e {sub forced} at the mean motion n {sub 0}, and oscillations at higher frequencies forced by the non-axisymmetric components of the binary’s potential. We show that accurate numerical values for the amplitudes and frequencies of these terms can be extracted from numerical orbit integrations by applying fast Fourier transformation (FFT) to the cylindrical distance between the circumbinary object and the center of mass of the binary as a function of time. We apply this method to three Kepler circumbinary planets and the satellites of Pluto-Charon. For the satellite Styx of Pluto-Charon, the FFT results for κ {sub 0} and e {sub free} differ significantly from the first-order analytic value and the value reported by Showalter & Hamilton, respectively. We show that the deviation in κ {sub 0} is likely due to the effect of the 3:1 mean-motion resonance and discuss the implications of the lower value for e {sub free}.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1985

The detection of eclipses in the Pluto-Charon system

The first eclipses between Pluto and its satellite ('Charon') were detected in January and February 1985, confirming the satellite's existence. Eclipses lasting a few hours will now occur at 3.20 day intervals for the next 5 to 6 years and then will cease for about 120 years. Careful observations of these eclipses will allow greatly improved determinations to be made of several physical parameters for the Pluto-Charon system: the diameters of the planet and satellite, the surface albedo distribution on one hemisphere of the planet, the orbit of the satellite, and the mass of the planet and hence its density. Knowledge of the density will provide a constraint on models of Pluto's bulk composition.

Binzel, R. P.↗

NASA NTRS1986

Satellites of Uranus and Neptune, and the Pluto-Charon system

The orbital properties, surface compositions, opposition surges, masses, radii, and densities of the satellites of Uranus are presented. It is noted that the Uranian satellites are comparable in size to the largest of Saturn's icy satellites while density measurements suggest that the bulk compositions of Ariel and Umbriel might be different from those of Titania and Oberon. Consideration is given to the two satellites of Neptune and the question of a third satellite is addressed. The elements of Charon, determined from astrometric observations by photographic and speckle interferometric techniques, and then from eclipse observations, are given. The diurnal period of Pluto and its photometric lightcurve are discussed. The similarities and differences existing between the satellites of Uranus and Neptune and the Pluto-Charon pair are mentioned briefly.

Cruikshank, Dale P.↗

NASA NTRS1987

IRAS constraints on the sizes of Pluto and Charon

Thermal emission models indicate that Charon contributes a significant amount of the infrared radiation detected by IRAS during the observation of mutual eclipse events. The IRAS observations also show that the most probable diameters for Pluto and Charon are 2200 and 1300 (+ or - 150) km. These results are consistent with there being some atmosphere on Pluto.

Tedesco, Edward F.↗

NASA NTRS1987

IRAS serendipitous survey observations of Pluto and Charon

On Aug. 16, 1983, the Infrared Astronomical Satellite made two separate pointed observations of Pluto and its moon Charon. Because of the small angular displacement of the system between the times of measurement, the Pluto-Charon system was identified as a source in the Serendipitous Survey (SSC 14029+0518). Detections were made at 60 and 100 micrometers with color-corrected flux densities of 581 + or - 58 and 721 + or - 123 millijanskys, respectively. Pluto is best described as having a dark equatorial band, and brighter polar caps of methane ice extending to + or - 45 deg latitude, at most. An upper limit of approximately 9 meter-amagats is placed on the column abundance of a methane atmosphere on Pluto, which is comparable to recent upper limits based on independent ground-based spectroscopy.

Sykes, Mark V.↗

NASA NTRS1988

The separate spectra of Pluto and its satellite Charon

The March 3, 1987 occultation of Charon by Pluto was observed spectroscopically from 5400 to 10,200 A at a resolution of 12 A. The midpoint of the event occurred at 11:06 UT; the depth of the event at 6800 A was 0.162 mag. The spectrum of Charon is completely featureless and almost perfectly flat; the red slope and the CH4 absorption features can be attributed solely to Pluto.

Fink, Uwe↗