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Davies A.G.,Jet Propulsion Laboratory | Veeder G.J.,Bear Fight Institute | Matson D.L.,Jet Propulsion Laboratory | Johnson T.V.,Jet Propulsion Laboratory
Icarus | Year: 2012

Using the NIMS Io Thermal Emission Database (NITED), a collection of over 1000 measurements of radiant flux from Io's volcanoes (Davies, A.G. et al. [2012]. Geophys. Res. Lett. 39, L01201. doi:10.1029/2011GL049999), we have examined the variability of thermal emission from three of Io's volcanoes: Pele, Janus Patera and Kanehekili Fluctus. At Pele, the 5-μm thermal emission as derived from 28 night time observations is remarkably steady at 37±10GWμm -1, re-affirming previous analyses that suggested that Pele an active, rapidly overturning silicate lava lake. Janus Patera also exhibits relatively steady 5-μm thermal emission (≈20±3GWμm -1) in the four observations where Janus is resolved from nearby Kanehekili Fluctus. Janus Patera might contain a Pele-like lava lake with an effusion rate (Q F) of ≈40-70m 3s -1. It should be a prime target for a future mission to Io in order to obtain data to determine lava eruption temperature. Kanehekili Fluctus has a thermal emission spectrum that is indicative of the emplacement of lava flows with insulated crusts. Effusion rate at Kanehekili Fluctus dropped by an order of magnitude from ≈95m 3s -1 in mid-1997 to ≈4m 3s -1 in late 2001. © 2012 Elsevier Inc.

Veeder G.J.,Bear Fight Institute | Veeder G.J.,Jet Propulsion Laboratory | Davies A.G.,Jet Propulsion Laboratory | Matson D.L.,Jet Propulsion Laboratory | And 3 more authors.
Icarus | Year: 2012

We have examined thermal emission from 240 active or recently-active volcanic features on Io and quantified the magnitude and distribution of their volcanic heat flow during the Galileo epoch. We use spacecraft data and a geological map of Io to derive an estimate of the maximum possible contribution from small dark areas not detected as thermally active but which nevertheless appear to be sites of recent volcanic activity. We utilize a trend analysis to extrapolate from the smallest detectable volcanic heat sources to these smallest mapped dark areas. Including the additional heat from estimates for " outburst" eruptions and for a multitude of very small (" myriad" ) hot spots, we account for ∼62×10 12W (∼59±7% of Io's total thermal emission). Loki Patera contributes, on average, 9.6×10 12W (∼9.1±1%). All dark paterae contribute 45.3×10 12W (∼43±5%). Although dark flow fields cover a much larger area than dark paterae, they contribute only 5.6×10 12W (∼5.3±0.6%). Bright paterae contribute ∼2.6×10 12W (∼2.5±0.3%). Outburst eruption phases and very small hot spots contribute no more than ∼4% of Io's total thermal emission: this is probably a maximum value. About 50% of Io's volcanic heat flow emanates from only 1.2% of Io's surface. Of Io's heat flow, 41±7.0% remains unaccounted for in terms of identified sources. Globally, volcanic heat flow is not uniformly distributed. Power output per unit surface area is slightly biased towards mid-latitudes, although there is a stronger bias toward the northern hemisphere when Loki Patera is included. There is a slight favoring of the northern hemisphere for outbursts where locations were well constrained. Globally, we find peaks in thermal emission at ∼315°W and ∼105°W (using 30° bins). There is a minimum in thermal emission at around 200°W (almost at the anti-jovian longitude) which is a significant regional difference. These peaks and troughs suggest a shift to the east from predicted global heat flow patterns resulting from tidal heating in an asthenosphere. Global volcanic heat flow is dominated by thermal emission from paterae, especially from Loki Patera (312°W, 12°N). Thermal emission from dark flows maximises between 165°W and 225°W. Finally, it is possible that a multitude of very small hot spots, smaller than the present angular resolution detection limits, and/or cooler, secondary volcanic processes involving sulphurous compounds, may be responsible for at least part of the heat flow that is not associated with known sources. Such activity should be sought out during the next mission to Io. © 2012 Elsevier Inc.

McCord T.B.,Bear Fight Institute | Castillo-Rogez J.,Jet Propulsion Laboratory | Rivkin A.,Laurel University
Space Science Reviews | Year: 2011

Ceres appears likely to be differentiated and to have experienced planetary evolution processes. This conclusion is based on current geophysical observations and thermodynamic modeling of Ceres' evolution. This makes Ceres similar to a small planet, and in fact it is thought to represent a class of objects from which the inner planets formed. Verification of Ceres' state and understanding of the many steps in achieving it remains a major goal. The Dawn spacecraft and its instrument package are on a mission to observe Ceres from orbit. Observations and potential results are suggested here, based on number of science questions. © Springer Science+Business Media B.V. 2011.

Davies A.G.,Jet Propulsion Laboratory | Veeder G.J.,Bear Fight Institute | Matson D.L.,Jet Propulsion Laboratory | Johnson T.V.,Jet Propulsion Laboratory
Geophysical Research Letters | Year: 2012

We have calculated the ≈5-μm radiant flux for every volcanic hot spot in every one of the 190 Galileo Near-Infrared Mapping Spectrometer (NIMS) tube observations of Io obtained between 28 June 1996 and 16 October 2001 in order to determine the variability of thermal emission from Io's volcanoes at local, regional and global scales, and to identify individual eruption episodes where thermal emission waxes and wanes. The resulting NIMS Io Thermal Emission Database (NITED) allows the comparison of activity at individual volcanoes and different regions of Io. The database contains over 1000 measurements of radiant flux at approximately 5 m, corrected for emission angle, range to target and incident sunlight (where necessary). We examine the data for Loki Patera, Io's most powerful volcano. For data acquired in local darkness we use two-temperature fits to nighttime spectra and prior knowledge of emitting area to determine total radiated thermal emission. For other data we use the constancy of the integrated thermal emission spectrum to determine total thermal emission from measurements of radiant flux at 5 m. As seen by NIMS, total thermal emission from Loki Patera varies between 7600 GW and 17000 GW. We revise upwards previous estimates of thermal emission from NIMS data. NIMS 3.5-m radiant fluxes (both measured and estimated) are consistent with measurements from ground-based telescopes. This work highlights the value of NITED as a research tool. copyright 2012 by the American Geophysical Union.

Wu Y.,Nanjing University | Besse S.,European Space Agency | Li J.-Y.,Planetary Science Institute | Combe J.-P.,Bear Fight Institute | And 3 more authors.
Icarus | Year: 2013

The main objective of this study is to develop a new photometric correction that is suitable for global Chang' E-1 (CE-1) Interference Imaging Spectrometer (IIM) data. We considered two improvements in the accuracy of the photometric correction: (1) classifying the whole Moon's surface into four classes (very bright rays, mature highlands, low FeO basalts, and high FeO basalts) based on the FeO contents; (2) decoupling the combined effects of the solar photometry and the detector responsivity along the cross-track. The results showed that our decoupling method could correct the non-uniformity of detector response but retain the cross-track photometry. Based on these in-flight calibrated data, spectrally continuous photometric functions of the four classes were obtained. By eliminating the contamination from highlands ejecta and low FeO basalts, the opposition surge of the high FeO maria was evident for the first time. The amplitude and width of the opposition surge presents wavelength dependence, which suggests that shadow hiding is the mechanism responsible for the opposition surge. A global lunar reflectance map whose boundaries between adjacent orbits are invisible was generated using the new four-type photometric functions. The quality of the global mosaic and the consistency of the reflectance spectra of the same area obtained in different orbits indicate the effectiveness of our photometric correction method. Although our method was specifically applied to the IIM data, the photometric correction method and the parameter values derived in this study is expected to be suitable for other optical instruments. © 2012 Elsevier Inc.

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