A new stereo topographic map of Io: Implications for geology from global to local scales

Abstract

We use Voyager and Galileo stereo pairs to construct the most complete stereo digital elevation model (DEM) of Io assembled to date, controlled using Galileo limb profiles. Given the difficulty of applying these two techniques to Io due to its anomalous surface albedo properties, we have experimented extensively with the relevant procedures in order to generate what we consider to be the most reliable DEMs. Our final stereo DEM covers~75% of the globe, and we have identified a partial system of longitudinally arranged alternating basins and swells that correlates well to the distribution of mountain and volcano concentrations. We consider the correlation of swells to volcano concentrations and basins to mountain concentrations, to imply a heat flow distribution across Io that is consistent with the asthenospheric tidal heating model of Tackley et al. (2001). The stereo DEM reveals topographic signatures of regional-scale features including Loki Patera, Ra Patera, and the Tvashtar Paterae complex, in addition to previously unrecognized features including an~1000 km diameter depression and a >2000 km long topographic arc comprising mountainous and layered plains material.

Topographic mapping of paterae and layered plains on Io using photoclinometry

“…We have not controlled our PC DEMs using stereo DEMs (which are themselves controlled using Galileo limb profiles [ White et al , ]). As we have described in section 1, PC is primarily useful for mapping local‐scale topography, but over larger distances, topographic undulations appear and the DEMs become progressively less reliable.…”

“…represents one of the best examples of a progression from a continuous unit of layered plains through fragmentation and eventual collapse, a sequence that is consistent with the results of previous studies that have interpreted layered plains to comprise heterogeneous mixtures of silicate-and sulfur-rich materials. The layered plains are isolated into plateaus by mass-wasting processes, with terraces representing discrete, heterogeneous layers that have been differentially eroded, and the scalloped morphologies of the scarps representing temporary erosional boundaries where the plains have been undermined through various processes such as sapping by pressurized, liquid SO 2 and gravity-driven slumping [Schaber, 1980;McCauley et al, 1979;Moore et al, 1996Moore et al, , 2001Schenk et al, 2001;Turtle et al, 2004;Davies, 2007;Williams et al, 2011].…”

“…In a recent publication [ White et al , ], we presented a new DEM covering ~75% of Io's surface that has been mosaicked using all available individual stereo DEMs derived from both Voyager and Galileo imagery and which have been controlled using Galileo limb profiles. We used this continuous topographic data set to identify the amplitudes and lateral extents of long‐wavelength variations in Io's global scale topography, as well as to identify previously undetected regional scale topographic structures and describe the topographic signatures of individual geological formations including Ra Patera, Loki Patera, and Tvashtar Paterae.…”

“…Due to the nature of the Voyager and Galileo stereo data sets on Io, we generally succeed in characterizing long‐wavelength, regional scale topography for a given stereo pair resolution, but in only a few cases, we do succeed in resolving small‐scale topographic features. This is especially true in the vertical dimension: only rarely do stereo DEMs achieve a vertical precision of a few hundred meters or less, much more commonly achieving several hundred meters to more than a kilometer [ White et al , ]. While this allows us to characterize the vertical reliefs of mountains (which frequently reach many kilometers high based on shadow measurements [ Schenk et al , ]), they are seldom able to resolve the topographic signatures of features such as paterae and layered plains (which typically display reliefs of several hundred meters to more than a kilometer based on shadow measurements, see Tables and in this paper), except in rare circumstances such as the Galileo stereo pair covering the Tvashtar Paterae complex, which achieves both good lateral resolution (320 m/pixel) and good vertical precision (350 m/pixel).…”

The geology of Pluto and Charon through the eyes of New Horizons

“…This technique has been successfully applied to the Galilean and saturnian satellites (e.g. [24][25][26][27][28][29], and we refer the reader to these references for detailed information on its construction and implementation. Stereo DEMs are reliable at regional scales, but are unable to resolve fine scale topographic features that are smaller than approximately five times the resolution of the poorest resolution image in the stereo pair due to pixel averaging.…”