Another instrument on Venus Express, VIRTIS (Visible and Infrared Thermal Imaging Spectrometer), can see below the clouds at infrared wavelengths. It detects the signature of sulphur dioxide by the amount of infrared radiation that the molecule absorbs, the stronger the signature, the more abundant the molecule.
The variation appears to be smaller in the lower atmosphere. With VIRTIS, we monitor sulphur dioxide at an altitude of 3540 km, and we have seen no change larger than 40% on a global scale over the last two years, says Giuseppe Piccioni, VIRTIS co-Principal Investigator, IASF-INAF in Rome.
The only way to be absolutely certain that active volcanism is taking place on Venus is to see a volcano in action. This is not easy when you are trying to look through 100 km of thick, cloudy atmosphere. But the Venus Express team are working on two ways of doing this. The first is to look for localised increases in sulphur dioxide that would indicate a large plume of the gas issuing from a volcano. The other way is to look for hot spots on the surface that can be shown to be fresh lava flows.
In both cases, the instrument to use is VIRTIS. No thermal anomaly has been detected so far, says Pierre Drossart, Observatoire de Paris, France, and co-Principal Investigator on VIRTIS. Nevertheless, the search continues and the team plan to announce their findings soon.
|Contact: Hkan Svedhem|
European Space Agency