Presentation Title

Quantitative measurements of active Ionian volcanoes in Galileo NIMS data

Start Date

November 2016

End Date

November 2016

Location

HUB 302-#185

Type of Presentation

Poster

Abstract

Io is the most volcanically active body in our solar system. The spatial distribution of volcanoes a planetary body’s surface gives clues into its basic inner workings (i.e., plate tectonics on earth). Hamilton et al. (2013) showed through a nearest neighbor analysis that hotspots are globally random, but regionally uniform near the equator. Lopes-Gautier et al. (1999) compared the locations of hotspots detected by NIMS to the spatial variation of heat flow predicted by two end-member tidal heating models. They found that the distribution of hotspots is more consistent with the heating occurring in asthenosphere rather than the mantle. Hamilton et al. (2013) demonstrate that clustering of hotspots also supports a dominant role for asthenosphere heating. Tidal heating is the major contributor to active surface geology in the outer solar system, and yet its mechanism is not completely understood. Io’s volcanoes are the clearest signature of tidal heating and measurements of the total heat output and how it varies in space and time are useful constraints on tidal heating. Furthermore, studies of the temporal variability of Ionian volcanoes have yielded substantial insight into their nature (Rathbun et al., 2002; Rathbun and Spencer, 2006; Davies, et al., 2006; Rathbun and Spencer, 2010; Davies and Ennis, 2011; Davis et al., 2012ab). The Galileo Near Infrared Mapping Spectrometer (NIMS) gave us a large dataset from which to observe active volcanic activity. NIMS made well over 100 observations of Io over an approximately 10-year time frame. With wavelengths spanning from 0.7 to 5.2 microns, it is ideally suited to measure blackbody radiation from surfaces with temperatures over 300 K. Here, we report on our effort to determine the activity level of each hotspot observed in the NIMS data. We decide to use 3.5 micron brightness as a proxy for activity level because it will be easy to compare to, and incorporate, ground-based observations (Rathbun et al., 2002). We fit a 1-temperature blackbody to spectra in each grating position and averaged the results to get a temperature and area (with uncertainties) for each pixel. From these results, we calculate 3.5 micron brightness (with uncertainties).

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Quantitative measurements of active Ionian volcanoes in Galileo NIMS data

HUB 302-#185

Io is the most volcanically active body in our solar system. The spatial distribution of volcanoes a planetary body’s surface gives clues into its basic inner workings (i.e., plate tectonics on earth). Hamilton et al. (2013) showed through a nearest neighbor analysis that hotspots are globally random, but regionally uniform near the equator. Lopes-Gautier et al. (1999) compared the locations of hotspots detected by NIMS to the spatial variation of heat flow predicted by two end-member tidal heating models. They found that the distribution of hotspots is more consistent with the heating occurring in asthenosphere rather than the mantle. Hamilton et al. (2013) demonstrate that clustering of hotspots also supports a dominant role for asthenosphere heating. Tidal heating is the major contributor to active surface geology in the outer solar system, and yet its mechanism is not completely understood. Io’s volcanoes are the clearest signature of tidal heating and measurements of the total heat output and how it varies in space and time are useful constraints on tidal heating. Furthermore, studies of the temporal variability of Ionian volcanoes have yielded substantial insight into their nature (Rathbun et al., 2002; Rathbun and Spencer, 2006; Davies, et al., 2006; Rathbun and Spencer, 2010; Davies and Ennis, 2011; Davis et al., 2012ab). The Galileo Near Infrared Mapping Spectrometer (NIMS) gave us a large dataset from which to observe active volcanic activity. NIMS made well over 100 observations of Io over an approximately 10-year time frame. With wavelengths spanning from 0.7 to 5.2 microns, it is ideally suited to measure blackbody radiation from surfaces with temperatures over 300 K. Here, we report on our effort to determine the activity level of each hotspot observed in the NIMS data. We decide to use 3.5 micron brightness as a proxy for activity level because it will be easy to compare to, and incorporate, ground-based observations (Rathbun et al., 2002). We fit a 1-temperature blackbody to spectra in each grating position and averaged the results to get a temperature and area (with uncertainties) for each pixel. From these results, we calculate 3.5 micron brightness (with uncertainties).