Our best knowledge of the Venusian surface comes from radar imaging, which can completely penetrate the cloud layers. Radar study of the terrain reveals intense volcanic activity and lava flows. The unexpectedly few number of meteor craters suggests that the entire surface melted about 500 million years ago.
It is believed that a lack of plate tactonics traps heat inside the planet. Instead of continuously releasing heat at plate-boundary zones, it may build up until catastrophic planet-wide events occur.
|Early radar views of Venus were made from earth-based antennas, such as the above image from the Goldstone radio telescope. The reflected radar chirp is doppler shifted by the rotation of the planet, and the return signals arrive sooner from nearer parts of the planet.|
|The best radar images come from orbiting probes such as Pioneer Venus, Venera 15 and Magellan. The image above is formed from Magellan data with some missing sections filled in with data from the other probes. Color indicates altitude.|
|Magellan produced images of very high resolution, such as this meteor crator. Features at high altitudes (and thus, lower temperature) appear brightly because radar is reflected by an electrically conductive material coating the surface. It is not known what that material is.|
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