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Eye on Io

first_imgJupiter’s volcanic moon Io continues to erupt, its heat flowing into science journals.  Planetary scientists are mapping its surface and devising new ideas about what drives its activity.    A paper in Icarus presented a new global geologic map of Io’s surface.1  The most common feature is plains (65.8%), followed by lava flow fields (28.5%, about a third of which are currently active), with a few mountains (3.2%) and patera floors (volcanic depressions, 2.5%).  These paterae account for 64% of Io’s hot spots.  The mountains and volcanoes appear evenly distributed by longitude, whereas there is a slight dropoff of lava flows in the polar regions.  This was the first complete map of Io from Galileo data at 1:15M scale (1 km per pixel).  Detailed surface mapping is essential for contemplating Io’s interior.    This little moon, about the size of Earth’s moon, is the most volcanically active body in the solar system (12/03/2007, 05/04/2004).  What makes it pop, with dozens of volcanoes active at a time, spewing out 100 times more lava than all Earth’s volcanoes combined?  A new theory by Krishan Khurana [UCLA] and a team from UCLA, UC Santa Cruz and University of Michigan at Ann Arbor is that Io has a global subsurface ocean of magma.  Space.com and PhysOrg featured the theory published in Science.2    The team inferred the presence of a global conducting layer based on magnetometer data from the Galileo mission.  They estimate that 20-30 miles below the crust, a layer of molten rock 30 miles deep produces the magnetic signature.  They did not address, however, questions about how the molten material erupts onto the surface without plate tectonics, or why heavy elements seen in the ultramafic lavas remain near the surface rather than having dropped deep into the interior billions of years ago.1.  Williams et al, “Volcanism on Io: New Insights from Global Geologic Mapping,” Icarus paper available online 05/13/2011, doi:10.1016/j.icarus.2011.05.007.2.  Khurana et al, “Evidence of a Global Magma Ocean in Io’s Interior,” Science Express, published online 12 May 2011.Stranger than Io’s volcanoes and the geysers of Enceladus is a phenomenon under the skulls of planetary scientists, where an unseen layer of liquid thought, worrying about how such activity could persist for billions of years, never seems to rise to the surface.(Visited 9 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img read more