Mapping Venus

25 Mar 2010

At www.physorg.com/print188466638.html March 22nd ... is another incredible piece of research. The article has a computer generated image of the surface of Venus created from radar images taken during NASAs Magellan mission during the 1990s. Peter James, a graduate student in the Earth and Planetary Sciences, has shown that plate tectonics do not seem to apply on Venus - or Mars and Mercury. The generation and restructuring of the surface of other rocky planets, including Venus, seems to occur through a process quite different to what happens on Earth. The Magellan images revealed a distribution of craters that suggested the surface of Venus was formed around the same time - 500 million years ago. This sounds like a very long time ago but it is much younger than the estimated age of the solar system - 4.6 billion years ago. As a result of the age of Venus scientists hypothesized that the surface is not made of moving plates nor was it inactive like the Moon. Instead, it is theorised that it evolved through periodic resurfacing.

To study the crust of Venus James used gravity and topography data from the Magellan mission  and was able to estimate the thickness of the crust, some 30km in comparison with the 20km of the Earth, and he identified those regions where the mantle is pulling at the crust as the planet cools. He also discovered there are no 'mascons' like those buried beneath the surface of the earth. These exist on Mars and the Moon as well as the Earth and are essentially gravity anomalies that correspond to large craters and basins created billions of years ago by massive impacts from large meteoroids. James had expected to find evidence of such structures and was surprised when that did not happen. He now thinks the absence of mascons is consistent with the idea that the surface of Venus experienced some kind of catastrophic restructuring at 500 million years ago - in order to erase mascons (which must have existed as the solar system is 4.6 million years old). Hence, he has managed to fit the evidence into the old concensus model - and there is no need to think in terms of Venus having an origin that is different to the other planets. Or is there? Other than that, this research is fabulous.