NASA scientists solve mystery of cracks in Europe




Analyzing notable cracks are lined with icy face of Europe, NASA scientists found evidence that the moon of Jupiter is probably turned on an inclined axis at some point. This shift could affect how much European history was written with ink ice, how much heat was formed by the tides of the oceans and how long the oceans remained liquid. This shift could also affect the estimate of the age of the ocean in Europe, 100 km depth.

Since it is assumed that the tidal forces generate heat, which store the oceans of Europe in the liquid state, the axis shift could mean that more heat is generated by tidal forces. So the oceans are extremely long can stay liquid.

“One of the mysteries of Europe – this is why the direction of the long straight cracks (hell) has changed over time. Quite possibly, a slight shift or tilt the axis of rotation axis once in the past can explain much of what we see, “- says Alyssa Roden of Oak Ridge Associated Universities, working with the Goddard Space Flight Center NASA. She is the lead author of the study.

Fracture network covering Europe, is a record of the stresses caused by the massive tides in the oceans of the moon. These tides occur because Europe is moving around Jupiter on a slightly oval orbit. As Europe moves closer to the planet, the moon is stretched like a rubber band, and the ocean rises to a height of about 30 meters. That’s roughly the same as it was in the Indian Ocean tsunami in 2004, only occurs on the body, which in size is one-quarter the diameter of Earth. When Europe gets farther from Jupiter, it shrinks back into ball shape.

The layer of lunar ice should stretch and bend to fit these changes, but when the stress becomes too great, it cracks. Riddle is why cracks over time are sent in different directions if Europe Jupiter constantly faces the same side.

A possible explanation could be that the frozen outer shell Europe rotating slightly faster than the moon itself – around Jupiter. If there is a non-synchronous rotation is not always one and the same part of the ice shell will look at Jupiter.

Roden and her co-author Terry Herford applied this idea in respect of photographs taken Galileo spacecraft during its eight-year mission, which began in 1995.

«Galileo caused a lot of paradigm shifts our understanding of Europe, one of which was the phenomenon of non-synchronous rotation” – says Claudia Alexander, of NASA’s Jet Propulsion Laboratory in Pasadena, the former head of the project upon completion of the mission Galileo.

Rodin and Herford compared pattern of cracks in one of the key areas near the equator Europe with predictions based on three different explanations. The first set of speculation was based on the rotation of the ice shell. The second thought that Europe revolves around a shifted axis, which, in turn, changes the pole position with a certain periodicity. This effect, called precession, is very similar to what happens when a toy spinning top begins to slow down and swing. A third explanation is that cracks occur in random directions.

Researchers have achieved the best results when suggested that the shift of one degree called precession, combined with some random cracks. Non-synchronous rotation of the model was highly unsuccessful, in part because Roden rechecked the original calculation of the model.

“If you remove the new information from the data of Galileo, this work refines and improves our understanding of the unusual geology of Europe” – said Richard Greenberg, a professor at Arizona State University, previously suggested the idea of ​​non-synchronous rotation.

The existence of the slope does not exclude non-synchronous rotation, and Rodin unanimously noted Greenberg. But it does suggest that the cracks of Europe could be much later than previously thought. Since the direction of rotation of the pole could be varied by more than two degrees per day, one in the precession period could be completed within a few months. On the other hand, one complete rotation of the ice sheet may occupy about 250 000 years. In any case, in order to explain the pattern of cracks, it is necessary to employ several rotations.

The analysis does not detect when there was a tilt axis. The slope of the axis of Europe are not measured, and it can become the number one goal for missions to Europe in the future.

“One of the fascinating open questions remains the extent to which Europe is active now. If researchers to bend axis modern Europe, our results allow to assess whether tips that we find on the surface of the moon, the current conditions, “- said Rodin.

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