NASA has the coolest toys. OK, sometimes they're not used for the most practical purpose. They're just cool. You can't have everything. In this arsenal of quasi useful, astoundingly exotic hardware is the THEMIS project. THEMIS for "Time History of Events and Macroscale Interactions during Substorms." Catchy, no? The name has been used before. Themis is the goddess of justice, wisdom and good counsel, the guardian of oaths, and the interpreter of the gods' will in Greek mythology.

THEMIS is a two-year mission with five identical satellites aimed at solving the riddle that is space substorms. In a display of Aurora Borealis, it is these substorms that cause the curtain of charged particles to shimmer and dance. Until now scientists guessed, but no one really knew what caused this extra part of the auroral show. To test a theory, the five THEMIS probes were positioned in a line directly down the Earth's magnetotail--a million kilometer long tail of magnetism pulled into space by the action of the solar wind. It wasn't long before the scientists were saying, "Duck! Plasma bullets are zinging past Earth."

This February the satellites detected a major explosion, not far from the center of their line, "releasing about 1015 Joules of energy," according to Vassilis Angelopoulos, the program's principal investigator. He continued, "For comparison, that's about as much energy as a magnitude 5 earthquake." This was the solar wind stretching the Earth's magnetic field and then letting go--allowing it to snap in much the same way you might shoot a rubber band. This in turn released two "plasma bullets," one heading toward Earth and the other away. As the energy crashed toward Earth a vivid aurora was spawned in far northern latitudes.

This was perfect positioning and perfect timing. There was too much preparation to write this off as luck.

"We had bulls-eyes on our solar panels," says THEMIS project scientist David Sibeck of NASA's Goddard Space Flight Center. "Four of the satellites were hit by the Earth-directed cloud, while the opposite cloud hit the fifth satellite." Simple geometry pinpointed the site of the blast between the 4th and 5th satellite or "about 1/3rd of the way to the Moon."

Is there a practical payoff for this science? Not that I can see, though I'm sure some justification can be conjured up in the astrophysical equivalent of Six Degrees of Kevin Bacon. That doesn't stop this mission from being very cool.