Galileo Provides Further Evidence of an Ocean on Europa

Galileo at Europa [10 Jan 2000] The Galileo spacecraft flew past Europa last week a scant 218 miles (351 km) above the surface. As it did, its magnetometer was looking to gain additional information on the moon's magnetic field. The spacecraft has apparently found that Europa's magentic field reverses its direction every 5 1/2 hours - something that is likely to happen only if there iss a salty water ocean beneath the ice - one capable of conducting electrical currents.

The results obtained clearly have the research team excited.

According to a NASA press release "I think these findings tell us that there is indeed a layer of liquid water beneath Europa's surface," said Dr. Margaret Kivelson, principal investigator for the magnetometer. "I'm cautious by nature, but this new evidence certainly makes the argument for the presence of an ocean far more persuasive."

The key to the interpretation derived from this data is the fact that solid ice is a very poor electrical conductor. In order for the observed changes in Europa's magnetic field to occur, something much more conductive than ice needs to be in place. A salty, water layer would fit the bill nicely.

Europa OrbiterAs it happens, photos taken by Galileo have shown Europa's surface to be a virtual traffic jam of colliding ice flows. These features point to a heat source that both causes ice to melt as well as drive the currents that moved large chunks of ice across the surface. Moreover, the relative lack of impact structures (craters) suggests that the surface of Europa is very, very young with some force at work that erases impacts rather swiftly (in geological terms).

As part of Galileo's recently extended mission, the spacecraft will make two flybys of Ganymede later this year. As is the case with Europa, Ganymede also shows evidence of a surface that has been rearranged by processes not unlike those at work on Europa. Callisto is also suspected of being shaped by these forces.

NASA is currently working on a mission to return to Europa and further explore the ocean it now seems have. As currently envisioned, the Europa Orbiter mission would be launched in 2003 and would place a spacecraft in orbit about Europa equipped with a laser altimeter, ice-penetrating radar, and high resolution imagery.

Once this mission has determined whether there actually is an ocean beneath Europa, (and if so, hope thick the ice is above it), the next step can be contemplated: sending a submarine to Europa.

° Galileo Findings Boost Idea of Other-Worldy Ocean, NASA press release
° Galileo Mission Status, 4 January 2000
° Galileo Swoops Flies Past Europa; Galileo Project to be Extended, SpaceRef
° Galileo Mission Extended, NASA JPL
° Galileo Website, NASA JPL
° Europa Orbiter Mission
° A Science Strategy for the Exploration of Europa Committee on Planetary and Lunar Exploration, National Research Council, 1999.

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