P41B-2057
Peeking into Saturn's Atmosphere: the HST Low-Phase Angle View
Thursday, 17 December 2015
Poster Hall (Moscone South)
Santiago Perez-Hoyos1, Jose Francisco Sanz-Requena2, Agustin Sanchez-Lavega1, Ricardo Hueso3, Teresa del Rio-Gaztelurrutia1, Jose F Rojas1, Amy A Simon4, Michael H Wong5, Imke De Pater5 and Patrick GJ Irwin6, (1)University of the Basque Country, Donostia, Spain, (2)Universidad Europea Miguel de Cervantes, Valladolid, Spain, (3)University of the Basque Country, Fisica Aplicada I, Donostia, Spain, (4)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (5)University of California Berkeley, Berkeley, CA, United States, (6)University of Oxford, Oxford, United Kingdom
Abstract:
Recent Hubble Space Telescope WFC3 observations of Saturn have provided a low-phase angle view of the planet that complements the higher phase angles and increased spatial resolution view from the Cassini spacecraft. HST orbits were perfectly timed for observing an atmospheric perturbation at polar latitudes that has been conspicuous on ground-based observations of the planet since May 2015. The observations serendipitously captured other interesting features at the Equatorial Zone (EZ) with Voyager-era fast speeds (see Sánchez-Lavega et al. abstract, this meeting). In this presentation we will discuss how the synergy between the Cassini/ISS and HST/WFC3 observations provides an excellent way for peeking into Saturn's atmosphere and analyze the vertical distribution and properties of the particles and aerosols located in the lower stratosphere and upper troposphere of the planet. We first discuss how Cassini/ISS observations at a variety of phase angles constrain particle properties and phase functions, in particular at the Equatorial Zone where they resemble 100 micron ammonia ice crystals. With this information, it is possible to use the HST/WFC3 observations at 10 filters from near-ultraviolet to the near-infrared provide substantial information on the vertical cloud structure and composition: the filters in and out of the intermediate and deep methane bands at the near infrared give information on particle number density around the tropopause level and down to the ammonia condensation level, while near-ultraviolet and blue filters characterize the absorption of unknown chromophores in Saturn's atmosphere. Fast-moving features in the EZ are found to be located deeper (> 2 bar) than the features used for cloud-tracking since the pre-Cassini era (< 1 bar). This provides an unprecedented view of the EZ vertical wind shear by sounding simultaneously three separate atmospheric levels. Finally, results for Saturn's Northern hemisphere will also be showed.
