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Liquid water on Europa

Galileo discovered evidence of water that may be under the ice sheet of Europa

Avi Blizovsky

NASA scientists have made the most powerful discovery that one of the mysterious moons of Jupiter harbors a raging ocean. The discovery was revealed on August 25, 2000 in the journal Science and is based on photographs sent to Earth by the Galileo spacecraft.
Europa, the fourth largest moon of Jupiter, has long been suspected of containing a very large amount of water. Since life as we know it requires water, this makes the moon a target for the search for extraterrestrial life.
If you place a compass on Europa, it will constantly rotate around itself in a way that is best explained by the presence of a layer of electrically conductive liquid, like salt water under ice. explains Dr. Margaret Kivelson, one of the five scientists involved in the article from the University of California, Los Angeles
(UCLA).

Kielson announced this conclusion when she first received the data from the magnetometer aboard Galileo after the spacecraft flew by Europa in January. The official article has now been published.
"We have good reasons to believe that the surface of Europa is made of water - frozen or even liquid," Kibleson said, pointing out that previous measurements of gravity have shown a low density, close to the density of water, in the regions
the exteriors of the moon. "But ice does not conduct so well, and therefore we believe that the conduction is carried out by a liquid ocean.
Galileo has flown by Europa frequently since it arrived in the Jupiter system in December 1995. Images from flights in which the spacecraft approached Europa show patterns that scientists see as evidence of a hidden ocean. In some of the photographs, ice barges appear to have changed position as they floated on liquid below them. In others the liquid appears to have risen to the surface and frozen.
However, these features can also be explained by the existence of an ocean in the past that froze and solidified, said Dr. Torrance Johnson, a scientist in the Galileo program who works at the Jet Propulsion Laboratory in Pasadena, California. The magnetometer data is just evidence that we have an ocean there now, rather than in the geologic past."
According to Johnson, the issue of the existence or non-existence of water flowing over Europe is still not closed. "The evidence is still indirect and several steps are required to reach the conclusion that we do have a salty ocean there," he says. "A definitive answer may come from precise tests of the lubrication field and height to examine the effect of the tide on the hypothesized ocean.
NASA plans to send a special spacecraft to Europa's moon, which will carry instruments that will be able to provide the necessary information. Magnetic evidence for the existence of an ocean is possible since Europa orbits Jupiter within Jupiter's magnetic field. The field provides an electromagnetic flux passing through the electrically conductive layers near Europa's surface, the current creating a sort of secondary magnetic field in Europa, the new report shows.
Galileo completed its original goals nearly three years ago, but it received an extension to its operation, and survived at radiation intensities three times stronger than those it was designed for.

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