Geologic implications of spectrophotometric measurements of Europa
Abstract
Detailed spectrophotometric measurements of Europa have been obtained from Voyager images of the satellite. Photometric functions and reflectances in four colors (ultraviolet, violet, blue, and orange) were derived for six mapped geologic terrains (plains and mottled terrains), three types of lineaments (wedge-shape, triple, and gray bands), and the brown spots. The geologic units fall into two clear colorimetric classes—red spectra of the dark brown spots and wedge-shaped bands and bluer spectra of the light plains. Classification by albedo also shows two end-member classes and a group with intermediate albedos (the mottled terrains and triple bands). These results suggest that there are two fundamental types of material on Europa: relatively clean ice making up the plains and darker, redder, silicate-rich material making up the brown spots and wedge-shaped bands. The pristine plains material has undergone progressive darkening by the infilling of fractures with the silicate-rich material to form the mottled terrains. Profiles of reflectance across the wedge-shaped bands and triple bands indicate that in some cases similar albedo and color changes occur for the two classes of bands, implying similar types of structures for both features. Many wedge-shaped bands may be triple bands whose bright central stripes are below the limit of resolution of the Voyager images.
- Publication:
-
Icarus
- Pub Date:
- September 1988
- DOI:
- 10.1016/0019-1035(88)90156-X
- Bibcode:
- 1988Icar...75..437B
- Keywords:
-
- Europa;
- Planetary Geology;
- Satellite Imagery;
- Satellite Surfaces;
- Spectral Reflectance;
- Spectrophotometry;
- Astronomical Photometry;
- Planetary Composition;
- Voyager 2 Spacecraft