A. Sánchez-Lavega

Temporal behavior of cloud morphologies and motions in Saturn's atmosphere

Saturns atmosphere displays a variety of temporal changes in its cloud morphology at synoptic and planetary scales. Hemispheric long-term albedo variations, which are more pronounced at ultraviolet and blue wavelengths, have been well established and are apparently linked to the seasonal insolation cycle. Short-term changes, of the order of months, have been observed in the spectral reflectivity of the belt/zone pattern mainly at mid-latitudes. Some appear to be related to discrete spot activity, but for the majority of the changes, no such signs of spot activity were detected up to a resolution ∼2000 km. In particular, the “ribbon” structure at 45°N could have been affected by this activity and probably is a transient phenomenon. The polar belts at ∼65° north and south and those at 75° north (hexagon) and south show a long-term stability in their location, perhaps for more than a century. The most prominent belts located in the Equator and the Equatorial Zone are persistent features of Saturns globe; their main changes took place during the development of a rare, planetary-scale disturbance known as Great White Spots. Only five such events have been observed at repetitive regular intervals of about one Saturn year since the first report in 1876, and at different latitudes from the equator to 60°N. They are probably convective in origin, with the seasonal heating of the upper atmosphere acting as a trigger mechanism. During its life cycle of 2–3 years, the disturbance shows turbulent planetary-scale patterns of clouds that might be related to a wave dynamical phenomenon. Other distinct nonaxisymmetric cloud systems at synoptic scale are very scarce in Saturns atmosphere. We observed new isolated features at several latitudes during 1990 and 1991. These spots, together with those available from historical records, are used as tracers for determining the latitude dependence and time variability of Saturns zonal winds. The winds tend to exhibit a long-term stability in their latitudinal positions and average wind speed, although some significant departures from the zonal mean Voyager profile have been detected during the development of the equatorial disturbance in 1990 and 1991.

Temporal and spatial variations of the absolute reflectivity of Jupiter and Saturn from 0.38 to 1.7 μm with PlanetCam-UPV/EHU

Aims. We provide measurements of the absolute reflectivity of Jupiter and Saturn along their central meridians in filters covering a wide range of visible and near-infrared wavelengths (from 0.38 to 1.7 μ m) that are not often presented in the literature. We also give measurements of the geometric albedo of both planets and discuss the limb-darkening behavior and temporal variability of their reflectivity values for a period of four years (2012–2016). Methods. This work is based on observations with the PlanetCam-UPV/EHU instrument at the 1.23 m and 2.2 m telescopes in Calar Alto Observatory (Spain). The instrument simultaneously observes in two channels: visible (VIS; 0.38–1.0 μ m) and short-wave infrared (SWIR; 1.0–1.7 μ m). We obtained high-resolution observations via the lucky-imaging method. Results. We show that our calibration is consistent with previous independent determinations of reflectivity values of these planets and, for future reference, provide new data extended in the wavelength range and in the time. Our results have an uncertainty in absolute calibration of 10–20%. We show that under the hypothesis of constant geometric albedo, we are able to detect absolute reflectivity changes related to planetary temporal evolution of about 5–10%.

Venus Spectrophotometry During the MESSENGER Mission Fly-By

The NASA mission MESSENGER fly-byed planet Venus on June 2007 on its route to Mercury. This chance was took to produce coordinated observations between Messenger and ESA Venus Express spacecrafts. This work shows spectra in the wavelength range between 320 and 1450nm retrieved with the instrument MASCS (Mercury Atmospheric and Surface Composition Spectrometer). Spectra are calibrated in absolute reflectivity (diffuse reflection by Venus clouds) and wavelength, and they are navigated in order to retrieve their position in the planet’s disk. Comparing synthetic spectra with these ones for each viewing geometry we will obtain information on the vertical distribution of cloud particulates between 60 and 75km height, approximately, as well as the SO2 abundance, among others. This will be combined with almost simultaneous data gathered by the visible and infrared spectrograph VIRTIS onboard Venus Express spacecraft. The results of the atmospheric modeling will be presented elsewhere.

Dynamics and Clouds in Jupiter Equatorial Zone

In this work we show a study of the dynamics and clouds in the equatorial zone of Jupiter. The studied area is wider than the pure Equatorial Zone ranging from the southern limit of the South Equatorial Belt (SEB) to the northern limit of the North Equatorial Belt (NEB). We have used images from the Cassini flyby in December 2000 (wavelengths of 752 and 939 nm) and from the Galileo orbiter taken in 1999 and 2001 (wavelengths of 559 and 756 nm). When needed we have used images from the International Outer Planet Watch database to complete the time coverage of the dataset. In visible wavelengths the study of the dark-bluish regions in the northern limit of the NEB that corresponds to the infrared hot spots show that they have the characteristics of a Rossby wave and can be explained as some Rossby wave induced effect. Nevertheless trying to explain the smaller and more abundant dark marks situated on the southern limit of the SEB in the same way has proven to be much more difficult. We will also describe our measurements of an anticyclonic white oval situated near the SEB dark marks. Finally we will present three train gravity waves that we have found in Galileo maps near the Equator.

Observations of Interactions between Giant Vortices in the Atmosphere of Jupiter: 1997–2000

We present a comparative observational perspective of unique phenomena that took place in recent years: the interaction and merger between the largest vortices present in the atmosphere of Jupiter.