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quote:Originally posted by SimmerI wonder if the Moon could have something to do with it - indirectly I mean through stirring up the mantle material or tidally preventing divergent plate boundaries from healing up?
Originally posted by neilepI don't suppose this is an easy question to answer but I would be very interested in your theories (in plain english if poss please) as to why our humble blue marble of a planet is the only one in the solar system that currently has moving tectonic plates.Thanks, your Down To Earth comments would be most welcome.Hi Neilep,what about icy moons such as Saturn's Enceladus ?:-http://news.bbc.co.uk/2/hi/science/nature/4197686.stmor Jupiter's moon Europa ?:-http://www2.jpl.nasa.gov/galileo/images/europa/eurridge-fracture.htmlThey seem to have moving sheets of ice, analogous to Earth's plates of rock.
quote:Originally posted by ROBERTwhat about icy moons such as Saturn's Enceladus ?:-http://news.bbc.co.uk/2/hi/science/nature/4197686.stmor Jupiter's moon Europa ?:-http://www2.jpl.nasa.gov/galileo/images/europa/eurridge-fracture.htmlThey seem to have moving sheets of ice, analogous to Earth's plates of rock.
quote:Originally posted by hogebI actually took a course in graduate school called the Comparative Paleoclimatology of the Terrestrial Planets which centered on this very question. In short, Venus is different from the earth because there is no water in its rocks. Why there is no water is not understood, but without it plate tectonics screech to a halt. Mars has had plate tectonics in its past, but doesn't now because its core has cooled. There must be a heat engine to drive plate tectonics. The fact that Mars is slightly cooler than the earth is thought to be the reason for its cooling, though it may be much more complicated than that. Lord Kelvin once calculated the age of the earth by predicting how long it would take a molten planet to cool to the earth's current temperature and came up woefully short because he didn't account for radioactivity in the core and mantle. I don't recall the rate of Mars cooling, but I seem to remember it took about two billion years for mars to cool.
quote:This represents the first conclusive evidence of plate tectonics in the Solar System beyond the Earth.
quote:On the Earth, the sea floor spreads apart slowly at mid-oceanic ridges as new crust flows up from Earth's hot interior. Meanwhile, the direction of Earth's magnetic field reverses occasionally, resulting in alternating stripes in the new crust that carry a fossil record of the past hundreds of million years of Earth's magnetic history, a finding that validated the once-controversial theory of plate tectonics. "The discovery of this pattern on Mars could revolutionize current thinking of the red planet's evolution," said Dr. Jack Connerney of NASA's Goddard Space Flight Center, Greenbelt, MD, an investigator on the Global Surveyor's magnetometer team. "If the bands on Mars are an imprint of crustal spreading, they are a relic of an early era of plate tectonics on Mars. However, unlike on Earth, the implied plate tectonic activity on Mars is most likely extinct." Alternate explanations for the banded structure may involve the fracturing and breakup of an ancient, uniformly magnetized crust due to volcanic activity or tectonic stresses from the rise and fall of neighboring terrain. "In order to call this pattern a crustal spreading center like that observed in the mid-oceanic ridges on Earth, we need to find a point of symmetry, where the pattern on one side matches the pattern on the other. We have not yet found evidence of this type of symmetry,"