Jupiter will rise at 7:14 this evening about six degrees south of due east. Although the eastern sky will be dominated by the full moon, Jupiter will be its second brightest object, much brighter than anything else nearby.
Look at Jupiter with a small telescope or good binoculars anytime before 10:48 p.m. and you will see all four of the moons discovered by Galileo in 1610. Europa will be about three Jupiter diameters above and to the right of the planet.
In one version of classical myth, Europa was the daughter of Aegenor, king of Phoenicia. Zeus, who had an eye for young women, was attracted by her beauty. Taking the form of a white bull, he abducted her and carried her away from Phoenicia to Crete. Minos, one of the three sons she bore him there, later became the island's king.
Europa is slightly smaller than our moon and nearly twice as far from Jupiter as our moon is from Earth. Europa orbits the giant planet once every 85 hours.
Like nearby Io, Europa's interior appears to be mostly silicate rock, but it probably lacks the iron core responsible for Io's significant magnetic field. Before the 1979 Voyager flyby, terrestrial telescopes had shown that Europa's surface was covered mostly with water ice.
Astronomers were nevertheless surprised by the Voyager photographs of Europa's face. This moon of Jupiter turns out to have the solar system's flattest surface, with features that appear strikingly similar to those of the pack ice covering Earth's Arctic Ocean. Moreover, instruments carried by the Galileo spacecraft detected weak and variable magnetic fields around Europa, fields of the type that might be generated by electric currents flowing through salty water.
It turns out that everything we have so far seen or measured on Europa is consistent with the existence of a relatively warm and salty subsurface ocean of liquid water, perhaps 50 to 100 miles deep, lying at most a few miles beneath its icy crust. It is this ocean's surprising presence that makes Europa rival the planet Mars as a possible haven for extraterrestrial life.
But getting down there to look for it is not going to be easy.
Jon Nance is a professor emeritus at Southwest Missouri State University.
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