P53C-01 INVITED
New Horizons At Jupiter: Overview Of Results
NASA's New Horizons spacecraft has provided new data on the Jupiter system, acquiring new perspectives of the giant planet's atmosphere, rings, moons and magnetosphere. These new views include the closest look yet at the Earth-sized "Little Red Spot" storm churning materials through Jupiter's cloud tops; detailed images of small satellites herding dust and boulders through Jupiter's faint rings; and of volcanic eruptions and circular mega- troughs on the planet's largest moons. New Horizons came to within 2.3 million kilometers of Jupiter on February 28 of this year, using the planet's gravity to trim three years from its travel time to Pluto. For several weeks before and after this closest approach, the spacecraft trained its seven instruments on Jupiter and its four largest moons, storing data from nearly 700 observations and gradually sending that information back to Earth. New Horizons completed its visit to the Jupiter system with its unprecedented flight down Jupiter's enormous magnetotail. The presentation will cover a number of Jupiter system studies - observations such as Jovian meteorology, studies of the great and little red spots, auroral studies, and magnetospheric sampling. Surface mapping, compositional mapping and atmospheric studies of Jupiter's largest moons are to be covered as well. A detailed report of the findings for the volcanic moon Io will be given in a companion presentation.
P53C-02 INVITED
New Horizons at Jupiter: From Polar Lightning to Equatorial Waves
Enroute to Pluto, the New Horizons encounter with Jupiter in January-March 2007 produced stunning new views and revelations about jovian dynamic meteorology. The sharpest multi-spectral global views ever obtained in the near-infrared revealed spectroscopically-identified ammonia clouds (SIACs) near 30 degrees south latitude, the first such detection of discrete ammonia clouds southward of the Great Red Spot. Movies of these clouds obtained over four jovian days revealed their rapid development and dissipation, consistent with a lifetime for SIACs of a few days. Winds within the Little Red Spot (LRS) measured by the LORRI telescopic imager were found to be comparable to those of the Great Red Spot. High spatial-resolution multi-spectral visual imagery by the MVIC camera revealed detailed 3-D views of the LRS and turbulence in the southern hemisphere. The turbulent wake region northwest of the Great Red Spot was found to be quiescent, absent the dynamic cloud systems observed over the previous 28 years by the Voyager, Galileo, and Cassini spacecraft. Compared to previous spacecraft views, a significant thinning of clouds is reported for the southern half of the Equatorial Region. Mesoscale wave structures are observed at low latitudes at a spatial resolution of about 11 km with LORRI, yielding a longitudinal wavelength of 300 km and a 100 m/s phase velocity relative to the zonal flow, much higher than had been predicted. Lightning was discovered at both poles, the first such optical detection of polar lightning for any planet beyond the Earth. The mean polar lightning radiative flux is found to be comparable to that previously reported for the mid-latitudes and significantly greater than reported for the equatorial region, consistent with internal heating being the main driver of convection on Jupiter.
P53C-03 INVITED
Observations of Jupiter Supporting the New Horizons Encounter and During a Period of "Global Upheaval"
Observations of Jupiter were made between February and June of 2007 to provide an expanded spectral coverage and timeline for the New Horizons remote-sensing of Jupiter's atmosphere. From March to May, two prominent vertical jets in the southern portion of Jupiter's North Temperate Belt (NTBs) initiated a major darkening of this region, and their wakes restored the darker color of the belt but not its bright 5-micron appearance. A brightening of the southern component of the dark South Equatorial Belt (SEBs) was interrupted by a series of vertical outbursts from which a darker material emanated in both directions was appeared bright at 5 microns.It also generated a series of anticyclonic vortices with upwelling interiors and substantial downwelling annuli which continue to this writing.
P53C-04
Near-Infrared Spectral Analysis of 2007 Jovian North Temperate Belt Disturbance
Jupiter has been experiencing an era of atmospheric global upheaval since 2005, with various localized and axisymmetric changes occurring all over the planet. We focus on the near-infrared spectra of the North Temperate Belt disturbance (NTBs), at latitude of 22 degrees north. The outbreak, identified late March 2007 as a bright feature high in the atmosphere, quickly encircled the planet in about two months. Near-infrared spectra of the feature were acquired with a medium-resolution near-infrared spectrometer, SpeX, at the NASA/Infra Red Telescope Facility (IRTF) on May 1-2, 2007. The feature dissipated within days thereafter. The 15 x 0.8 arc sec slit spectra were spatially resolved into sub apertures along the spectral slit (1.0 x 0.8 arc sec), allowing us to geometrically register the spectral data for the discrete feature, without losing data integrity. Our preliminary results indicate the presence of ammonia ice, similar to the spectrum of ammonia clouds identified in Galileo/Jupiter data (Baines et al. 2002, Icarus, 159). The strength of the ammonia ice features varies from the localized "head" of the feature along the length of the slit (i.e., longitude). Our results will be compared with the results with (1) spectral analysis of other regions of Jupiter that have not undergone such dramatic changes to determine the differences between them and (2) other spectra obtained from NASA/IRTF and Lick Observatory with The Aerospace Corporation's visible/near-infrared spectrometer VNIRIS to determine the temporal evolution of NTBs disturbance and (3) compare with spectra of other disturbances such as those currently occurring in the South Equatorial Belt (SEB).
P53C-05
New Horizons Alice UV Observations of a Stellar Occultation by Jupiter's Atmosphere
The Alice instrument onboard the New Horizons spacecraft observed two occultations of Chi Ophiuchus by Jupiter's atmosphere during the 2007 Jupiter flyby. The ingress occultation probed the atmosphere at 35 degrees latitude (planetographic) near the dawn terminator, while the egress probed 20 degrees latitude near the dusk terminator. We present a preliminary analysis of both the ingress and egress occultations, including determinations of the methane and acetylene homopause levels. These observations provide stringent constraints for the assumed strength of eddy mixing in current photochemical models of Jupiter's atmosphere.
P53C-06
Icy Galilean Satellite UV Observations by New Horizons and HST
The New Horizons (NH) spacecraft observed the icy Galilean satellites with the Alice instrument during the Jupiter flyby in spring of 2007. Hubble Space Telescope Advanced Camera for Surveys (ACS) far-ultraviolet images of Europa and Ganymede complement the Alice UV spectroscopy at this time. Europa and Ganymede OI 130.4 nm and 135.6 nm emissions were detected. Alice observed Ganymede in eclipse twice, viewing the sub-Jupiter and anti-Jupiter hemispheres separately. The ACS Ganymede images show limb brightened emissions from auroral ovals on the leading and trailing sides, consistent with previous Space Telescope Imaging Spectrograph (STIS) imaging. The ACS Europa image shows a localized emission feature similar in extent to a feature previously observed with STIS. Callisto's FUV albedo spectrum was also observed. Preliminary results will be presented.
P53C-07 INVITED
New Horizons at Jupiter: Observations of Io
Jupiter's volcanic moon Io was a prime target for the New Horizons spacecraft during its early 2007 Jupiter flyby. 190 grayscale images, 17 color images, and 7 near-infrared image cubes, and numerous ultraviolet spectra were taken during the flyby in order to map changes in surface appearance, volcanic plumes, and hot spots since the last close-up observations, by Galileo in late 2001. Best imaging resolution was about 12 km/pixel. The result was the most comprehensive global snapshot of Io volcanism yet obtained. Numerous small surface changes were seen along with several large changes, including new pyroclastic deposits associated with two major new lava flows in the southern hemisphere. Several new volcanic plumes were seen, but several plumes first seen by the Voyager spacecraft in 1979 continue to be active. Most dramatic was a 330 km high plume from the Tvashtar volcano, which provided the most detailed view yet of a large Pele-class Io plume. The plume maintained similar size and appearance for eight days, displaying a bright top and little evidence for a column of upgoing particles, suggesting that most visible particles condense out of the plume gases during flight rather than being ejected directly from the vent. Intricate filamentary structure in the plume allows direct tracking of plume motions, revealing projected speeds up to 0.7 km s-1. Images of Io in Jupiter eclipse show visible-wavelength auroral glows from all plumes and also very localized emission from most surface volcanic features near the sub-Jupiter and anti-Jupiter hemispheres, a phenomenon seen previously by Galileo. The glows do not correlate with infrared thermal emission, suggesting that a non-thermal process is illuminating gas tens of kilometers above volcanos in these locations.
P53C-08
Monitoring Io volcanism with AO telescopes during and after the NH flyby
To support the New Horizons (NH) Jupiter encounter we monitored Io's volcanic activity using high angular resolution images in the near infrared (1-5 microns) provided by adaptive optics (AO) systems available on 8-10m class telescopes. We initiated the campaign on Feb. 25 2007 with data obtained with the VLT-Yepun telescope (ESO, Paranal, Chile), just before NH closest approach. We continued monitoring with the Gemini North telescope (Hawaii, USA). The last observation was taken on May 28 2007. Numerous active volcanoes are visible in the data but the Tvashtar eruption is by far the most energetic. Extremely high angular resolution data from NH revealed fine detail of the eruption, such as the presence of an active plume [1]. This volcano has an interesting past history. It was seen as a powerful eruption from Nov. 26 1999 during the Galileo I25 [2] flyby to Feb. 19 2001 from the ground [3]. It was dormant or below our ground-based limit of detection (T<330 K assuming an area of 460 km2) between Dec 2001 and May 2004 [4,5]. The re-awakening of the volcano was reported by Laver et al. [6] in April 2006 based on Keck Adaptive Optics (AO) observations. Our last Gemini AO observation taken on May 26 shows that Tvashtar was still very active. Based on the previous behavior of this volcano [7] it is very likely that the activity reported in 2007 is a continuation of the Tvashtar-2006 eruption. Other hot spots, such as Loki Patera, Pele, and a new hot spot located north of Loki Patera, were seen in our data. We will describe the global picture of Io's volcanic activity derived from our observations, comparing it with previous observations from the Galileo spacecraft and using ground-based AO. 1. Spencer et al., AGU, this session, 2007 2. McEwen et al., Science, 288, 1193-1198, 2000 3. Marchis et al. Icarus, 160, 124-131, 2002 4. Marchis et al., Icarus, 176, 1, 2005 5. Marchis et al., AGU Fall meeting, V33C-1483, 2004 6. Laver et al., Icarus, in press, 2006 7. Milazzo et al., 2005, Icarus, 179, 235–51