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We present in this Keck AO paper the first global high angular resolution observations of Io in three broadband near-infrared filters: Kc (2.3 mu m), Lp (3.8 mu m), and Ms (4.7 mu m). The Keck AO observations are composed of 13 data sets taken during short time intervals spanning 10 nights in December, 2001. The MISTRAL deconvolution process, which is specifically aimed for planetary images, was applied to each image. The spatial resolution achieved with those ground-based observations is 150, 240, and 300 km in the Kc, Lp, and Ms band, respectively, making them similar in quality to most of the distant observations of the Galileo/NIMS instrument. Eleven images per filter were selected and stitched together after being deprojected to build a cylindrical map of the entire surface of the satellite. In Kc-band, surface albedc, features, such as paterae (R > 60 km) are easily identifiable. The Babbar region is characterized by extremely low albedo at 2.2 mu m, and shows an absorption band at 0.9 mu m in Galileo/SSI data. These suggest that this region is covered by dark silicate deposits, possibly made of orthopyroxene. In the Lp-Ms (3-5 mu m) bands, the thermal emission from active centers is easily identified. We detected 26 hot spots in both broadband filters over the entire surface of the minor planet; two have never been seen active before, nine more are seen in the Ms band. We focused our study on the hot spots detected in both broadband filters. Using the measurements of their brightness, we derived the temperature and area covered by 100 brightness measurements. Loki displayed a relatively quiescent activity. Dazhbog, a new eruption detected by Galileo/NIMS in August 2001, is a major feature in our survey. We also point out the fading of Tvashtar volcanic activity after more than two years of energetic activity, and the presence of a hot, but small, active center at the location of Surt, possibly a remnant of its exceptional eruption detected in February 2001. Two new active centers, labeled F and V on our data, are detected. Using the best temperature and the surface area derived from the L and M band intensities, we calculated the thermal output of each active center. The most energetic hot spots are Loki and Dazhbog, representing respectively 36 and 19% of the total output calculated from a temperature fit of all hot spots (20.6 x 10(12) W). Based on the temperature derived from hot spots (similar to 400 K), our measurement can unambiguously identify the contribution to the heat flux from the silicate portion of the surface. Because the entire surface was observed, no extrapolation was required to calculate that flux. It is also important to note that we measured the brightness of the individual hot spots when they were located close to the Central Meridian. This minimizes the line-of-sight effect which does not follow strictly a classical cosine law. Finally, we argue that despite the widespread volcanic activity detected, Io was relatively quiescent in December 2001, with a minimum mean total output of 0.4-1.2 W m(-2). This output is at least a factor of two lower than those inferred from observations made at longer wavelengths and at different epochs. (c) 2005 Elsevier Inc. All rights reserved.

Io, the innermost Galilean satellite of Jupiter, is a fascinating world. Data taken by Voyager and Galileo instruments have established that it is by far the most volcanic body in the Solar System and suggest that the nature of this volcanism could radically differ from volcanism on Earth. We report on near-IR observations taken in February 2001 from the Earth-based 10-m W. M. Keck II telescope using its adaptive optics system. After application of an appropriate deconvolution technique (MISTRAL), the resolution, ~100 km on Io's disk, compares well with the best Galileo/NIMS resolution for global imaging and allows us for the first time to investigate the very nature of individual eruptions. On 19 February, we detected two volcanoes, Amirani and Tvashtar, with temperatures differing from the Galileo observations. On 20 February, we noticed a slight brightening near the Surt volcano. Two days later it had turned into an extremely bright volcanic outburst. The hot spot temperatures (> 1400 K) are consistent with a basaltic eruption and, being lower limits, do not exclude an ultramafic eruption. These outburst data have been fitted with a silicate-cooling model, which indicates that this is a highly vigorous eruption with a highly dynamic emplacement mechanism, akin to fire-fountaining. Its integrated thermal output was close to the total estimated output of Io, making this the largest ionian thermal outburst yet witnessed. Key Words: Io; volcanism; infrared observations.

The temperature excesses and Ly-alpha bulge in the jovian upper atmosphere of Jupiter is characterized. Specifically, the possibility that the planet's aurorae control the atmosphere's dynamics and energy is advanced through the theory that thermospheric winds 'collide at the jovian equator near 100 degrees longitudinal system II.' This collision, in turn, leads to energy conversion and kinetic energy transfer to the northern and southern jets. The latter's thermal energy accounts for the heating excess over the whole planet.

A reanalysis of the limb to limb Lyman-alpha reflectivities using the revised H Lyman-alpha sensitivity for the Voyager 1 instrument provides a coherent set of ultraviolet spectral data. The limb to limb Lyman-alpha reflectivities are determined with the Voyager UVS instruments. The reanalysis considers four different sources for the origin of Lyman-alpha radiation in the planets. The reanalysis reveals that UV emissions are not caused by strong atmospheric turbulence or a collisional excitation source.

We present ground-based observations of the jovian ionospheric [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] emission at 4 micrometers, using the CSHELL facility long-slit spectrograph at the NASA Infrared Telescope Facility (IRTF) in Hawaii. The data were obtained during four consecutive nights from July 13 to July 16, 1996. The 30-arcsec length slit of the spectrograph was aligned with the jovian CML, in order to get high-spatial, high-spectral resolution latitudinal profiles of the jovian [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] emission. A self-consistent multi-emission-component (MEC) model, developed for the analysis of these latitudinal profiles, simulates the emission from the vertical distribution of the ionization components known to produce [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. We initially identify these as solar-EUV photo-ionization, auroral oval precipitation, and diffuse auroral precipitation. A fourth component, mid-to-low (MTL)-latitude ionization is derived, and then fitted. InfraRed [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] auroral ovals follow closely the UV ovals as observed with the HST instruments WFPC2 and FOC. Our model shows that the auroral production rate is generally between a few and a few tens of times the EUV rate. The MTL component production rate is 1 to 40% of the auroral rate in the north, and 2 to 16% in the south. Input and output energies are scaled to solar EUV values. We assume an EUV insolation of 60 [micro]W/[m.sup.2], equivalent to a total jovian EUV insolation of [10.sup.12]W. Scaled to the EUV input, planetwide integration of the components of our model produces the total hemispheric energy inputs associated with the aurora, the diffuse emission, and the MTL emission. The results are 1.22([+ or -] .25) x [10.sup.12]W, 0.37([+ or -] .15) x [10.sup.12]W, and 0.65([+ or -] .32) x [10.sup.12]W, respectively, for the north and 1.15([+ or -] .30) x [10.sup.12]W, 0.21([+ or -] .10) x [10.sup.12]W, and 0.64 ([+ or -] .32) x [10.sup.12]W for the south, respectively. We discusss the limitations of our scaling process, introducing the notion of emission efficiency with respect to a nominal 1000K/LTE [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] emitter. The overall auroral emission is approximately 43 (+107, -23)% of that measured in 1993. Our results show that [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] controls the energy balance of the auroral regions above the homopause, as well as the equatorial regions. [C] 2000 Academic Press