Tuesday, July 14, 2009

New map hints at Venus's wet, volcanic past

The first temperature map of the planet's southern hemisphere at infrared wavelengths, charted with Venus Express's Visible and Infrared Thermal Imaging Spectrometer, VIRTIS. The new map hints that our neighbouring world may once have been more Earth-like, with a plate tectonics system and an ocean of water. The map comprises over a thousand individual images, recorded between May 2006 and December 2007, from a distance of about 60 000 km. Because Venus is covered in clouds, normal cameras cannot see the surface, but Venus Express used a particular infrared wavelength that can see through them.

The new data are consistent with suspicions that the highland plateaus of Venus are ancient continents, once surrounded by ocean and produced by past volcanic activity. The map is centred at the South Pole. The measured temperatures range from 442°C (or 715K), red to 422°C (or 695K) blue; higher temperatures correspond to lower altitudes, while lower temperature correspond to higher altitudes. The temperature difference is key to understanding whether Venus is volcanically active today. However, a 'flux anomaly' may be related to temperature difference and to different surface emissivity.



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