Jovian moon Callisto may hide a salty ocean

   Jupiter's second largest moon, Callisto, may have a liquid ocean tucked under its icy, cratered crust, according to scientists studying data gathered by NASA's Galileo spacecraft. The Galileo findings, published in the Oct. 22 issue of the journal Nature, reveal similarities between Callisto and another of Jupiter's moons, Europa, which has already displayed strong evidence of a subsurface ocean. "Until now, we thought Callisto was a dead and boring moon, just a hunk of rock and ice," said Dr. Margaret Kivelson, space physics professor at the University of California at Los Angeles (UCLA) and principal investigator for Galileo's magnetometer instrument, which measures magnetic fields around Jupiter and its moons. The salty ocean premise was inspired by Galileo data indicating that electrical currents flowing near Europa's surface cause changes in Europa's magnetic field. "This seemed to fit nicely with other data supporting the idea that beneath Europa's icy crust, a liquid ocean might be serving as a conductor of electricity," said Kivelson.

   Armed with that information, Kivelson and UCLA colleagues Drs. Krishan K. Khurana, Raymond J. Walker, and Christopher T. Russell set out to test a similar theory about Callisto.  The team went back and studied data obtained during Galileo's flybys of Callisto in November 1996, and June and September of 1997. Kivelson and her colleagues found signs that Callisto's magnetic field, like Europa's, is variable, which can be explained by the presence of varying electrical currents associated with Jupiter that flow near Callisto's surface. Their next challenge was to discover the source of the currents. "Because Callisto's atmosphere is extremely tenuous and lacking in charged particles, it would not be sufficient to generate Callisto's magnetic field; nor would Callisto's icy crust be a good conductor, but there very well could be a layer of melted ice underneath," Kivelson said.

Dark-Suckers
courtesy of Jim Brown

For years it has been believed that electric light bulbs emit light, but recent discoveries suggest otherwise.  Light bulbs don't emit light; they suck dark.  Rather than calling them light bulbs, we should be calling them Dark-Suckers.  The Dark-Sucker Theory holds that dark has mass and is heavier and faster than light.

For example, take the Dark-Sucker in the room with you now. There is much less dark right next to it than there is elsewhere.  The larger the Dark-Sucker, the greater its capacity for sucking dark.  Dark-Suckers in a shopping center parking lot have a lot more capacity for sucking dark than the ones in your living room.

As with all things, Dark-Suckers don't last forever.  Once they are full of dark, they can no longer suck.  (Tip: Look for the dark spot on a full Dark-Sucker.)

A candle is a primitive form of Dark-Sucker.  A new candle has a white wick.  After the first use, the wick turns black, representing all the dark that has been sucked into it.  If you put a pencil next to the wick of an operating candle, it will turn black.  This is because it got in the way of dark flowing into the candle.

There are also portable Dark-Suckers.  In these, the bulbs can't handle all the dark by themselves and must

be aided by a Dark Storage Unit.  When the Dark Storage Unit is full, it must either be emptied or replaced before the portable Dark-Sucker will work again.

Dark has mass.  When dark goes into a Dark-Sucker, friction from the moving mass generates heat.  Candles are even worse because the dark must travel into a solid wick instead of through clear glass.  This generates a great amount of heat.  Never touch an operating Dark-Sucker or candle.

Dark is heavier than light.  If you were to swim just below the surface of a lake, you would see a lot of light.  If you were to slowly swim deeper and deeper, you would notice it getting darker.  When you reached really great depths, you would be in total darkness.  This is because the heavier dark sinks to the bottom of the lake, while the lighter light floats at the top.  This is where light got its name.

Dark is faster than light.  If you were to be in a room full of light, standing in front of a closed, dark closet, and slowly opened the closet door, you would see the light slowly enter the closet.  But since dark is so fast, you would not be able to see the dark leaving the closet. Try it.

So, the next time you encounter a so-called light bulb, remember that it is really a Dark-Sucker.

Page 7        Prime Focus  November 1998  Next Page  Previous Page