WorldCat Identities

Spencer, John R. (John Robert) 1957-

Works: 5 works in 29 publications in 2 languages and 1,344 library holdings
Genres: Observations 
Roles: Editor, Author, Other
Classifications: QB723.S56, 523.64
Publication Timeline
Most widely held works by John R Spencer
The great comet crash : the impact of comet Shoemaker-Levy 9 on Jupiter( Book )

8 editions published in 1995 in English and held by 851 WorldCat member libraries worldwide

Tells the story of comet Shoemaker-Levy 9, from its discovery in March, 1993, to its break-up in Jupiter's atmosphere in July, 1994. Includes information on comets and the findings of the scientific community about the crash
Io after Galileo : a new view of Jupiter's volcanic moon by Rosaly M. C Lopes( Book )

17 editions published between 2006 and 2007 in English and German and held by 128 WorldCat member libraries worldwide

Reviews the basics about Io and it's space environment. This book includes various subjects, where the Galilio mission shed light on, with emphasis on several of Io's characteristics including it's active volcanism. It is intended for planetary scientists and volcanologists in general, and newcomers wishing to specialize in this field of research
The surfaces of Europa, Ganymede, and Callisto : an investigation using Voyager IRIS thermal infrared spectra (Jupiter) by John R Spencer( )

2 editions published in 1987 in English and held by 3 WorldCat member libraries worldwide

Modelling of surface water ice migration gives a possible explanation for the inferred lateral inhomogeneities on Ganymede. Dirty ice surfaces at Jupiter are subject to segregation into high-albedo ice-rich cold spots and ice-free regions covered in lag deposits, on decade timescales. Ion sputtering and micrometeorite bombardment are generally insufficient to prevent the segregation. The reflectance spectra of Ganymede and Callisto may be consistent with this type of segregated surface
Prediction of cleaning results of dense media operations by John R Spencer( )

1 edition published in 1979 in English and held by 1 WorldCat member library worldwide


in English and held by 0 WorldCat member libraries worldwide

In 1979, the IRIS infrared spectrometers on the two Voyager spacecraft obtained over 1000 disk-resolved thermal emission spectra of Europa, Ganymede, and Callisto, Jupiter's three large icy satellites. This dissertation describes the first detailed analysis of this data set. Ganymede and Callisto subsolar temperatures are 10°K and 5°K respectively below equilibrium values. Equatorial nighttime temperatures are between 100°K and 75°K, Callisto and Europa being colder than Ganymede. The diurnal temperature profiles can be matched by 2-layer surfaces that are also consistent with the eclipse cooling observed from earth, though previous eclipse models underestimated thermal inertias by about 50%. Substrate thermal inertias in the 2-layer models are a factor of several lower than for solid ice. These are 'cold spots' on Ganymede and Callisto that are not high-albedo regions, which may indicate large thermal inertia anomalies. All spectra show a slope of increasing brightness temperature with decreasing wavelength, indicating local temperature contrasts of 10-50°K. Callisto spectra steepen dramatically towards the terminator, a trend largely matched with a laterally-homogeneous model surface having lunar-like roughness, though some lateral variation in albedo and/or thermal inertia may also be required. Subsolar Ganymede spectra are steeper than those on Callisto, but there is no steepening towards the terminator, indicating a much smoother surface than Callisto's. The spectrum slopes on Ganymede may indicate large lateral variations in albedo and thermal inertia. A surface with similar areal coverage of dark, very low thermal inertia material, and bright material with thermal inertia a factor of 2-3 below solid ice, fits the diurnal and eclipse curves, and (less accurately) the IRIS spectrum slopes. Europa spectra have very small slopes, indicating a smooth and homogeneous surface. Modelling of surface water ice migration gives a possible explanation for the inferred lat
Audience Level
Audience Level
  Kids General Special  
Audience level: 0.34 (from 0.31 for The great ... to 0.77 for The surfac ...)

The great comet crash : the impact of comet Shoemaker-Levy 9 on Jupiter
Alternative Names
Spencer John R. 1957-....

Spencer, John Rason

Spencer, John Robert

Spencer, John Robert 1957-

English (27)

German (2)

Io after Galileo : a new view of Jupiter's volcanic moon