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  • Kansas Legislator Proposes Bill to Outlaw Sustainability Education
    A bill has been introduced in the Kansas legislature this week that would prohibit the promotion of ...Read more

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    Kansas Legislator Proposes Bill to Outlaw Sustainability Education

    A bill has been introduced in the Kansas legislature this week that would prohibit the promotion of sustainability. Here is a link to the one-page bill: http://www.kslegislature.org/li/b2013_14/measures/documents/hb2366_00_0000.pdf. See report on Bloomberg News.
  • Earth's Center Is 1,000 Degrees Hotter Than Previously Thought, Synchrotron X-Ray Experiment Shows
    Scientists have determined the temperature near the Earth’s center to be 6000 degrees Celsius, 1000 ...Read more

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    Earth's Center Is 1,000 Degrees Hotter Than Previously Thought, Synchrotron X-Ray Experiment Shows

    Scientists have determined the temperature near the Earth’s center to be 6000 degrees Celsius, 1000 degrees hotter than in a previous experiment run 20 years ago. These measurements confirm geophysical models that the temperature difference between the solid core and the mantle above, must be at least 1500 degrees to explain why the Earth has a magnetic field. For more information about this study, see the press release from the European Synchrotron Radiation Facility.
  • Ocean Volcanic Rocks Contain Samples of Recycled Crust
    Scientists have long believed that lava erupted from certain oceanic volcanoes contains materials fr...Read more

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    Ocean Volcanic Rocks Contain Samples of Recycled Crust

    Scientists have long believed that lava erupted from certain oceanic volcanoes contains materials from the early Earth’s crust. But decisive evidence for this phenomenon has proven elusive. New research from a team including Carnegie’s Erik Hauri demonstrates that oceanic volcanic rocks contain samples of recycled crust dating back to the Archean era 2.5 billion years ago. Their work is published in Nature. Oceanic crust sinks into the Earth’s mantle at so-called subduction zones, where two plates come together. Much of what happens to the crust during this journey is unknown. Model-dependent studies for how long subducted material can exist in the mantle are uncertain and evidence of very old crust returning to Earth’s surface via upwellings of magma has not been found until now. For more information about these results, see the press release from the Carnegie Institution.
This is a composite image of three of the Galilean satillites.
Click on image for full size
NASA

Evolution of Icy Moons

The three moons to the left illustrate three possible stages in the history of an icy satellite. The satellite can be cold and so have no internal activity. In that case, the surface is unchanged, old, and heavily cratered. This case may be illustrated by Callisto, the top moon in the picture. The craters are left over from the formation of the moon itself, 4 billion years ago. Nothing has happened to this moon to ever change its surface appearance.

If there was some internal heating, then the surface may show some changes and will not be as heavily cratered. This case may be illustrated by Ganymede, the moon in the middle of the picture. Ganymede has many craters but also trenches and grooves which indicate that the surface flowed at some point in time.

If the heating took place over a long time, then the surface may show many changes, and in fact may still be evolving. This case may be illustrated by Europa, the third moon in the picture. The surface of Europa is lightly cratered with evidence of cracks and fractures.

Many moons in the solar system exhibit features of evolution somewhere between those of Ganymede and those of Europa. Examples of these moons include Dione, Rhea, Enceladus, Tethys, Ariel, Umbriel, Miranda, Titania, Oberon, and Triton.

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Ice can flow inside an icy satellite

This is a picture of ice flowing at the south pole, or the Antarctic region of the Earth. Ice flows very easily, but very slowly. Glaciers are perfect examples of the fact that ice can move. Glaciers flow...more

The Surface of Dione

The surface of Dione does not have many craters. Instead it has wispy white streaks similar to those found on Rhea extending for many kilometers over the entire surface. These two things indicate that...more

The Surface of Rhea

The surface of Rhea is typical of an icy moon. Rhea is as heavily cratered (despite the appearance of this picture) as Saturn's "death star" moon Mimas on its leading side. Its trailing side has unusual...more

The Surface of Enceladus

The surface of Enceladus does not have many craters. Instead it has grooves similar to those found on Ganymede. These grooves extend for many kilometers over the surface. The presence of grooves indicates...more

The Surface of Tethys

The surface of Tethys is heavily cratered, which means that the surface is very old and hasn't been changed. Tethys is more lightly cratered in one region, however. This may be a sign of some internal...more

Surface of Umbriel

The surface of Umbriel seems to be like many icy moons. It appears to have many craters, but is not as heavily cratered as Callisto. ...more

Surface of Miranda

The surface of Miranda is very unusual. It is not like any other moon in the solar system. Miranda has many craters but also very big grooves. These indicate that there has been activity inside Miranda...more

Surface of Titania

The surface of Titania is like many icy moons. It appears to be changed for it does not have many craters. Instead it has grooves and ridges similar to those found on Ganymede. These grooves e xtend for...more

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The Spring 2011 issue of The Earth Scientist is focused on modernizing seismology education. Thanks to IRIS, you can download this issue for free as a pdf. Print copies are available in our online store.

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