Loki Patera is an active volcanic feature on Jupiter's moon Io which, at approximately 200 km in diameter, is perhaps the largest active lava lake in the solar system. Several images taken by the narrow angle camera of Voyager 1 during its 1979 flyby of Io reveal the patera surface is populated with many bright features roughly 2 to 4 km in diameter, colloquially referred to as "bergs." The bergs may be gas vents, similar to terrestrial fumaroles, which allow the sulfur-rich volatiles in the lava beneath the solid patera crust to escape and deposit on the surface. This thesis examines the spatial distribution of the bergs and their spectral signature in comparison with other features in the Loki region. The spectral analysis specifically focuses on the brightness in the blue and violet filters in an attempt to determine their composition and better understand how the bergs are related to the volcanic activity observed at Loki.
The spatial distribution analysis reveals that the bergs are not randomly distributed across the patera surface and they avoid the inner and outer margins of the patera. There are no bergs within 4.96 km of the outer margin and only one berg occurs closer than 4.02 km to the inner margin. The bergs also avoid each other; bergs are on average 5.34 km from each other, and there is little deviation from this mean aside from the bergs in the southwest corner, which are spaced further apart. This corner has fewer bergs than elsewhere in the patera and is the site of the most volcanic activity.
Data from the Voyager and Galileo missions were included in the spectral analyses. Assuming a macroscopic mixture, the spectral signature of the bergs indicate compositions ranging from bare basalt in the southwestern portion of the patera to approximately 43% sulfur and 57% basalt for the bergs. Other features around Loki, such as the large island in the middle of the patera, have slightly different brightnesses in the blue and violet filters which may indicate the presence of some SO 2 in addition to sulfur.
There is evidence that a few of the largest bergs were not resurfaced between the Voyager and Galileo observations, suggesting some bergs may be fixed features. The bergs may be sulfur volatiles deposited on top of large mounds in the patera which could form during resurfacing events. One type of terrestrial lava mound, tumuli, typically have a linear crack running along the axis of the mound. If the bergs are a much larger version of tumuli seen on Earth, the axial fissure could provide a route for volatiles beneath the crust to escape onto the surface and deposit around the opening.
|Advisor:||Howell, Robert R.|
|Commitee:||Montague, Derek, Sims, Kenneth W.|
|School:||University of Wyoming|
|Department:||Geology and Geophysics|
|School Location:||United States -- Wyoming|
|Source:||MAI 52/01M(E), Masters Abstracts International|
|Keywords:||Io, Jupiter, Loki, Spectroscopy, Volatiles, Volcanology|
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