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Flagstaff, AZ, United States

Mount C.P.,Arizona State University | Titus T.N.,Astrogeology Science Center
Journal of Geophysical Research E: Planets | Year: 2015

Small-scale variations of seasonal ice are explored at different geomorphic units on the Northern Polar Seasonal Cap (NPSC). We use seasonal rock shadow measurements, combined with visible and thermal observations, to calculate density over time. The coupling of volume density and albedo allows us to determine the microphysical state of the seasonal CO2 ice. We find two distinct end-members across the NPSC: (1) Snow deposits may anneal to form an overlying slab layer that fractures. These low-density deposits maintain relatively constant densities over springtime. (2) Porous slab deposits likely anneal rapidly in early spring and fracture in late spring. These high-density deposits dramatically increase in density over time. The end-members appear to be correlated with latitude. Key Points Albedo and density are used to constrain evolution of seasonal CO2 ice There are two seasonal CO2 end-members Conceptual models are developed for each end-member. © 2015 American Geophysical Union. All Rights Reserved.

Tsang C.C.C.,Southwest Research Institute | Rathbun J.A.,University of Redlands | Spencer J.R.,Southwest Research Institute | Hesman B.E.,University of Maryland University College | Abramov O.,Astrogeology Science Center
Journal of Geophysical Research E: Planets | Year: 2014

The New Horizons spacecraft flew past Jupiter and its moons in February and March 2007. The flyby provided one of the most comprehensive inventories of Io's active plumes and hot spots yet taken, including the large 350 km high eruption of Tvashtar. Among the suite of instruments active during the flyby was the Linear Etalon Infrared Spectral Array (LEISA), a near-infrared imaging spectrometer covering the spectral range 1.25 to 2.5 μm. We have identified 37 distinct hot spots on Io in the nine LEISA spectral image cubes taken during the flyby. We describe the thermal emissions from these volcanoes and fit single-component blackbody curves to the hot spot spectra to derive eruption temperatures, areas, and power output for the hot spots with sufficient signal-to-noise. Of these, 11 hot spots were seen by LEISA more than once, and East Girru showed short-term variability over a few days, also seen by other New Horizons instruments. This work presents a comprehensive look at the global distribution of Io's volcanism at the time of the flyby. From these measurements, we estimate the global power output of high-temperature (>550 K) volcanism on Io to be ~8 TW. This work provides the first short-wavelength near-infrared survey with global coverage at all longitudes on the nightside of Io without sunlight contamination at these wavelengths. A major conclusion from this study is that 90% of all the volcanoes observed in the New Horizons LEISA near-infrared data in 2007 were also observed during the Galileo epoch, suggesting these are all long-lived hot spots. © 2014. American Geophysical Union.

Rivkin A.S.,Johns Hopkins University | Marchis F.,Search for Extraterrestrial Intelligence Institute | Stansberry J.A.,US Space Telescope Science Institute | Takir D.,Astrogeology Science Center | And 3 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2016

The James Webb Space Telescope (JWST) provides the opportunity for ground-breaking observations of asteroids. It covers wavelength regions that are unavailable from the ground and does so with unprecedented sensitivity. The main belt and Trojan asteroids are all observable at some point in the JWST lifetime. We present an overview of the capabilities for JWST and how they apply to the asteroids as well as some short science cases that take advantage of these capabilities. © 2016. The Astronomical Society of the Pacific. All rights reserved.

Keszthelyi L.P.,Astrogeology Science Center | Jaeger W.L.,Astrogeology Science Center | Dundas C.M.,University of Arizona | Martinez-Alonso S.,University of Colorado at Boulder | And 2 more authors.
Icarus | Year: 2010

We provide an overview of features indicative of the interaction between water and lava and/or magma on Mars as seen by the High Resolution Imaging Science Experiment (HiRISE) camera during the Primary Science Phase of the Mars Reconnaissance Orbiter (MRO) mission. The ability to confidently resolve meter-scale features from orbit has been extremely useful in the study of the most pristine examples. In particular, HiRISE has allowed the documentation of previously undescribed features associated with phreatovolcanic cones (formed by the interaction of lava and groundwater) on rapidly emplaced flood lavas. These include "moats" and "wakes" that indicate that the lava crust was thin and mobile, respectively [Jaeger, W.L., Keszthelyi, L.P., McEwen, A.S., Dundas, C.M., Russel, P.S., 2007. Science 317, 1709-1711]. HiRISE has also discovered entablature-style jointing in lavas that is indicative of water-cooling [Milazzo, M.P., Keszthelyi, L.P., Jaeger, W.L., Rosiek, M., Mattson, S., Verba, C., Beyer, R.A., Geissler, P.E., McEwen, A.S., and the HiRISE Team, 2009. Geology 37, 171-174]. Other observations strongly support the idea of extensive volcanic mudflows (lahars). Evidence for other forms of hydrovolcanism, including glaciovolcanic interactions, is more equivocal. This is largely because most older and high-latitude terrains have been extensively modified, masking any earlier 1-10 m scale features. Much like terrestrial fieldwork, the prerequisite for making full use of HiRISE's capabilities is finding good outcrops.

Watters T.R.,Smithsonian Institution | Selvans M.M.,Smithsonian Institution | Banks M.E.,Smithsonian Institution | Hauck S.A.,Case Western Reserve University | And 2 more authors.
Geophysical Research Letters | Year: 2015

The surface of Mercury is dominated by contractional tectonic landforms that are evidence of global-scale crustal deformation. Using MESSENGER orbital high-incidence angle imaging and topographic data, large-scale lobate thrust fault scarps have been mapped globally. The spatial distribution and areal density of the contractional landforms are not uniform; concentrations occur in longitudinal bands and between the north and south hemispheres. Their orientations are generally north-south at low latitude to midlatitude and east-west at high latitudes. The spatial distribution and distribution of orientations of these large-scale contractional features suggest that planet-wide contraction due to interior cooling cannot be the sole source of global stresses. The nonrandom orientations are best explained by a combination of stresses from global contraction and tidal despinning combined with an equator-to-pole variation in lithospheric thickness, while the nonuniform areal density of the contractional features may indicate the influence of mantle downwelling or heterogeneities in lithospheric strength. ©2015. American Geophysical Union. All Rights Reserved.

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