Spectroscopic observations of Solar-System objects with ISO provided a wealth of new and exciting results. Major findings relevant to planetary atmospheres and surfaces are presented here. Rotational lines of HD were observed for the first time in the four giant planets, yielding reliable determinations of the D/H ratio. The 14N/15N ratio could also be measured in the upper troposphere of Jupiter. Many new hydrocarbons were detected in the giant planets, improving our understanding of the methane photochemistry. In addition, oxygen compounds (H2O and CO2) were detected in their upper atmospheres and in Titan, pointing to exogenic sources of oxygen. Many bands of SO2 ice were observed on Io, providing information on the physical state of this volcanic compound on the surface. Finally, spectra of Mars revealed the presence of a few so-far undetected mineralogical features, tentatively attributed to carbonates.

Three recent close flybys of Io by the Galileo spacecraft, and new observations from the Hubble Space Telescope and ground-based telescopes, have greatly advanced our understanding of Jupiter’s volcanic moon Io. Io’s volcanos are much hotter than previously suspected, perhaps requiring exotic silicate magma compositions. Despite much new data, Io’s largest volcano, Loki, is still poorly understood. New data on Io’s plumes suggest the existence of two types of plumes: primary plumes, relatively rich in S2 gas, which are emitted where magma first reaches the surface, and secondary plumes, more SO2 rich, which result from interaction of lava flows with a volatile-rich substrate.

The Near Infrared Mapping Spectometer (NIMS) on the Galileo spacecraft has been observing the volcanic Jovian satellite Io at regular intervals since June 1996. These infrared observations have allowed detailed mapping of the distribution and grain size of sulfur dioxide on Io’s surface, identification of volcanic centers, mapping of the distribution of hot spots, and investigations into the style and evolution of individual volcanic eruptions.

One of the premier areas of scientific return from Hubble Space Telescope (HST) observations of Solar System objects has been studies of the Galilean satellites of Jupiter. Because these objects are unresolvable in most ground-based observations, HST’s spatially resolved imaging and spectroscopy of their surfaces, atmospheres, and electrodynamic interactions with the Jovian magnetosphere have provided unique results. This talk will review highlights of the science results from HST observations of the Galilean satellites, including discovery of auroral emissions at the poles of Ganymede, the recent discovery of molecular sulfur in the Pele plume on Io, and the presence of SO2 in the surface of Callisto.

Analysis of data from the Galileo spacecraft continues to provide significant advances in our understanding of the geology and composition of Jupiter’s icy Galilean satellites Callisto, Ganymede, and Europa.

In 1994 the HST camera acquired images of Titan during 14 visits throughout a 16—day rotation period. These images were mosaicked to produce surface maps of albedo variations at several wavelengths (0.67, 0.94, and 1.04 microns) which revealed a bright, continent-sized feature on Titan’s leading face (Smith, Lemmon, & Lorenz 1996). Also, the observing program was designed as a search for clouds and their motions; no clouds were conclusively identified. Other observing sessions in subsequent years performed by our group and others have resulted in numerous observations through WFPC2, STIS, and NICMOS. Additional maps have now been made in the 2—micron region that show a very similar surface albedo to the 0.94—micron map (T. Owen, private communication). Models based on these data sets are used to understand the lower atmosphere and surface as seen through the overlying hazes; seasonal variations resulting in a north-south asymmetry of the haze layer are also being studied.

The first images of Titan at 1.3 micron were obtained with the PUEO adaptive optics system at the CFHT, on October 26 1998. We have also obtained images of Titan at 1.6 micron. Our diffraction-limited images (about 10 independent resolution elements or 20 pixels on the disk) pertain to Titan’s leading hemisphere. We have used narrow-band filters centered outside (1.29, 1.6 µm) and in the wings (1.18, 1.64 µm) of the methane bands, so as to be able to subtract the atmospheric contribution from our data. Images of Titan’s surface show the large equatorial region to be bright at both wavelengths. Combined with previous spectroscopic and imaging data, our findings are compatible with the presence of a mountainous plateau, covered with bright ice (perhaps methane), near the equator of Titan and with hydrocarbon deposits in the darker areas.

Saturn’s largest moon Titan is the only satellite in the Solar System with a substantial atmosphere. Photolysis of methane creates a hydrocarbon haze in Titan’s atmosphere that is opaque to visible light. The new adaptive optics system on the 10–meter W. M. Keck Telescope enables us to observe Titan with a resolution of 0.04 arcseconds, or 20 resolution elements across the disk. By observing at near-infrared wavelengths that are methane band windows we can see through Titan’s hydrocarbon haze to the surface beneath. Recent adaptive optics images of Titan both in broadband (J, H, and K) filters and in narrowband filters that selectively probe Titan’s surface and atmosphere allow us to determine surface albedo and properties of the hydrocarbon haze layer. Future observations will include high-resolution spectroscopy coupled with adaptive optics to obtain spectra of individual surface features.

Titan’s atmosphere potentially sports a cycle similar to the hydrologic one on Earth with clouds, rain and seas, but with methane playing the terrestrial role of water. Over the past ten years many independent efforts indicated no strong evidence for cloudiness until some unique spectra were analyzed in 1998 (Griffith et al.). These surprising observations displayed enhanced fluxes of 14-200% on two nights at precisely the wavelengths (windows) that sense Titan’s lower altitude where clouds might reside. The morphology of these enhancements in all 4 windows observed indicate that clouds covered ~6-9% of Titan’s surface and existed at ~15 km altitude.

Here I discuss new observations recorded in 1999 aimed to further characterize Titan's clouds. While we find no evidence for a massive cloud system similar to the one observed previously, 1%-4% fluctuations in flux occur daily. These modulations, similar in wavelength and morphology to the more pronounced ones observed earlier, suggest the presence of clouds covering ≤1% of Titan's disk. The variations are too small to have been detected by most prior measurements. Repeated observations, spaced 30 minutes apart, indicate a temporal variability observable in the time scale of a couple of hours. The cloud heights hint that convection might govern their evolution. Their short lives point to the presence of rain.

The Mars Global Surveyor (MGS) spacecraft entered an elliptical orbit at Mars on September 11,1997. Until March 1999 it acquired scientific data from decreasing-sized orbits as it alternated between aerobraking and nadir-pointing modes. This time period provided tremendous advances in our knowledge of the shape and topography, the gravity field, the magnetic field, and the atmospheric structure and dynamics of Mars. In April 1999 MGS entered its planned two years in the mapping mode. In this mode the high-gain antenna tracks Earth so that the instruments can take data continuously and so that the camera system can return high-resolution data in real-time. IR spectral and temperature data, as well as high-resolution images are providing new insight into the geologic evolution of Mars. All data is being archived at about six month centers so that it is available in electronic format to the international community.

The surface composition of Mars has been investigated using the Thermal Emission Spectrometer (TES) instrument during the mapping phase of the Mars Global Surveyor mission. The TES has mapped ~85% of the Martian surface at a resolution of 3-9 km. Separation of the atmospheric dust, water-ice cloud, CO2, water vapor, and surface components has been accomplished using radiative transfer and deconvolution. Two distinct surface compositional units have been mapped; (1) a basalt with plagioclase feldspar, Ca-rich pyroxene, minor sheet silicates; and (2) a basaltic andesite with silica glass, plagioclase, and minor pyroxene. Three large-scale (100’s km) accumulations of hematite have been found in Sinus Meridiani, Aram Chaos and Ophir/Candor Chasms. These regions are interpreted to be formed by aqueous precipitation under either ambient or hydrothermal conditions. No surfaces with detectable abundances of carbonate have been found. The albedo of the surface has been mapped with an absolute accuracy of ~1-2% and significant changes in surface albedo have occurred from the orbital measurements obtained by the Viking IRTM instrument.

Data collected by the Viking mission to Mars resulted in a picture of the Martian climate which stood largely unmodified for over a decade. When a challenge did come in the mid-1990’s it resulted from ground-based and HST observations which suggested lower global-average temperatures and dust opacities, and more atmospheric water ice than inferred from Viking. These observations prompted suggestions of climate change orders of magnitude larger and faster than anything contemplated for the Earth. A combination of new data from the Mars Global Surveyor Thermal Emission Spectrometer (TES) and reanalysis of Viking-era data have resulted in a new picture of the Martian climate. It is now clear that no significant climate change has occurred and that the “cooler and cloudier” conditions observed in the 1990’s for northern summer applied equally well to the Viking era. TES observations have provided detailed information on the cycle of air temperature and water ice clouds which support and extend the ground-based and HST observations. The disagreement with Viking observations has been found to result from faults in the Viking Orbiter Infrared Thermal Mapper (IRTM) 15 µm channel, the lack of analysis of IRTM data applicable to water ice, and the misinterpretation of Viking Lander opacity measurements. The TES observations provide a rich data base which is now allowing a new picture of the Martian climate to be constructed in which water vapour and water ice clouds may play a significant role in modulating the annual cycles of dust and air temperature.

Thermal emission spectra from the MGS TES instrument permit retrieval of atmospheric properties that are of interest in the study of Martian meteorology, including temperature, dust, and water ice. Examples of analyses of zonal mean meridional thermal sructure for equinox and solstice conditions are presented.

A space mission to Mars’ moon Phobos with a space vehicle of new generation currently developed by the Russian Aerospace Agency is discussed. The vehicle design incorporates innovative SEP technology focused on small propulsion electric engines which significantly improve the mission energetic capability. The project is optimized around a sample return (PSR) from Phobos and also offers an opportunity for rendezvous/sample return missions from several asteroids, comets, and NEO. Scenario, rationale, and basic profile of PSR mission are presented.

The digitization of the planetary database of IAU has been performed, to give access to historical data in digital format. The database is constituted from the planetary photograph center collections, which was organized in 1961 at the request of the IAU (IAU conferences; Last reference: 1979, IAU Trans., XVIIA, 109). From this collection, 8473 images have been digitalized and are now accessible on line in a compressed format at the Web address: http://bdipwww.obspm.fr. The catalog information, including date and time of observations, and geometric configuration is completed for Jupiter and Saturn. The database contains plates recorded between 1870 and 1977:

Jupiter: 2715 images

Saturn: 357 images

Mars: 4661 images

Venus: 835 images

Mercury: 105 images

Short–exposure images of Mercury were recorded at the Abastumany astrophysical observatory. A single image, with low distortion, is shown and discussed with respect to Mariner 10 observations.

We study the opposition effect of icy planetary satellites by means of a Monte Carlo simulation of the coherent backscattering opposition effect for spherical objects covered with locally plane parallel media.

Observations with HST WFPC-2 from 1994 to 1997 show a number of features which can be attributed to the surface (notably the large as-yet-unnamed bright region, several smaller bright areas and a number of dark regions). The delineation of these features in several datasets is presented. Other features are variable and are due to atmospheric phenomena: these include the total brightness of Titan (drop by 5% 1994-1997 at 350 nm; increase by 7% at 889 nm), the hemispheric north-south asymmetry, and the hint of a south polar hood.

Additionally, small variable features, apparently due to clouds, are documented. As well as variability from one year to the next, these show anomalous center-to-limb brightness behaviour, and a 673/940 nm color much bluer than the large surface feature, consistent with clouds in the troposphere.

Jupiter’s North Equatorial Belt (NEB) occasionally undergoes cycles of activity that consist of rapid broadening of the dark belt to the north, often accompanied by cyclonic bright “rift” activity, followed by development of large circulations in the expanded northern part (cyclonic dark “barges” and anticyclonic bright “portholes”), and a reddish colour across the belt (Rogers 1995). In 1996 there was a classic NEB broadening event with typical evolution over the following years. The broadening to the north began in 1996 April and spread around the belt by the summer. By 1997 April, there was an array of “barges” and “portholes” (white ovals) all around the broadened NEB, and increased redness of the belt. During 1997 the northern extension gradually reverted towards the normal bright albedo for this latitude, but the barges and ovals persisted. Indeed they still persist in 1999/00. Features in 1998/99/00 have included a rapidly-prograding white oval which destroyed barges ahead of it and had retrograding dark spots created following it; these retrograding spots have circulated as was observed in Voyager maps.

Due for launch in 2003 as part of the Mars Express mission, the primary goal of the Beagle 2 lander is the detection of extinct or extant life on Mars. Atmospheric studies, analysis of subsurface material and regime, and the first attempt at in-situ radiometric dating of rocks on another planet make Beagle 2 unique among planetary missions. The lander is named after Darwin’s ship, H.M.S Beagle.