Venus is shrouded in a thick cloud layer which hides the surface from any visual imaging. However during the Galileo-flyby a spectral window at 2.3µm in the near-infrared was used which allows to "see" down to the lowest cloud layer. Following theoretical studies have shown the existing of several spectral windows in the infrared range. The image on the right shows a comparison between Venusian topographie as derived from Pioneer Venus radar data with an image in the 2.3µm window obtained by NIMS on Galileo. Clearly visible are the "colder" mountain-tops on the "warm" lowlands.
VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) on Venus Express (VEX) is an imaging spectrometer (VIRTIS-M) for the visual (0.25-1µm) and the near-infrared range (1-5µm) combined with a high resolution IR-spectromter (VIRTIS-H) for the spectral range from 2-5µm.
Our main interest in VIRTIS on Venus Express is in the use of the spectral windows to study the low atmosphere and the surface directly. Through these windows we hope to obtain "images" of the surface with a spatial resolution of approx. 50km, While the Magellan radar data has a higher spatial resolution, it allows no direct interpretation of surface composition. VIRTIS will be the first instrument to use the near-infrared atmospheric windows for for a global mapping and a global study of the surface composition. Furthermore VIRTIS on Venus Express can be used to search for direct and tell-tale signs of active vulcanism. Lava erupting from a volcano will have a higher temperature then the surrounding surface. By searching for suddenly appearing, localized hotspots VIRTIS can search directly for volcanic activity. In addition during a volcanic eruption typical gases are released. A localized enrichment of these gases would ba a tell-tale sign of active volcanism. By combination of all data VIRTIS on Venus Express will be the first instrument capable of directly studying the surface atmosphere interaction on Venus on a global scale.
The work on VIRTIS is done in close collaboration with the Optical Information Systems department at DLR Adlershof, the IRSPS in Pescara, Italy and the University of Oulo, Finland.
More details on the surface science done with VIRTIS