A radiative transfer model of the Venus atmosphere and the search for active volcanism through Venus Express
- Paper number
IAC-05-A3.P.20
- Author
Mr. Constantine Tsang, University of Oxford, United Kingdom
- Coauthor
Prof. Fred Taylor, University of Oxford, United Kingdom
- Year
2005
- Abstract
Venus is a place of extremes. She is characterized by high surface temperatures and pressures ( sim740K, sim90bars), clouds of sulphuric acid and a super-rotating atmosphere. Venus Express will be arriving around this hostile environment in the first half of 2006. An orbiter derived from the Mars Express mission, Venus Express will be the first mission to Venus for ESA. It is carrying seven science instruments, most of which are devoted to analyzing the atmospheric properties of Venus. One of the ongoing questions this mission will try to answer is whether Venus is still active volcanically, a topic of intense debate for the last twenty years. If we can determine the level of activity on the surface and in the atmosphere, we will better understand the evolution of the climate on Venus. We can monitor for signs of active volcanism using two main methods; tracking trace gases such as sulphur dioxide, using a radiative transfer model, and using the near-infrared windows to probe the surface to look for infrared heat signatures from volcanoes.
Radiative transfer is the process of absorption and emission of radiation in a planets or stars atmosphere. Properties of the atmosphere and of the surface can be deduced by detecting this radiation. A radiative transfer model created at Oxford and used for retrieving properties of the Jovian planets have now been adapted to be used for Venus in preparation for the arrival of Venus Express in 2006. In addition, it has been known only relatively recently, that at the near infrared wavelengths, radiation can permeate from deep in the atmosphere, as far down as the surface. These near-infrared emission windows have been reproduced in the model. I will present results here to show the model calculations of what a volcanic eruption would look like through VIRTIS, the Visible and Infrared Thermal Imaging Spectrometer onboard Venus Express. Various volcanic plume profiles have been applied to the model, with variations in the viewing angle, orbit position and instrument modes. This should give us a better understanding to what style of eruption is best detectable and where in the orbit to do this successfully.
Finally, I present work concerning the mapping of surface temperature at near-infrared windows. We can see the surface of Venus at radar wavelengths, as excellently demonstrated by NASA’s Magellan orbiter in the early 1990s. However, we can also probe the surface at 1.01 mum and 1.18 mum emission windows, in the near-infrared. Because these windows are in the infrared, any abnormally high temperatures due to eruptions can be detected. I present cloud corrections and optical depths of clouds at these wavelengths, knowledge of which is critical if this method of detection is going to be successful.
- Abstract document