Why did China shoot down an aging weather satellite with a ballistic missile? And why has its government stayed silent about the incident for nearly two weeks?

These are among many questions raised by the first destruction of a satellite by any country since 1985. Both the United States and the Soviet Union successfully destroyed orbiting satellites, but stopped after the explosions scattered huge amounts of debris in space. So did the Chinese action early this month, possibly endangering other orbiting satellites.

Does the Chinese test signal an arms race in space? Or is it meant to prod others, Washington in particular, to get serious about negotiating a treaty to ban the militarization of space? Here's hoping it's the latter.

Some analysts speculate that China's senior leaders may have been aware of preparations for testing satellite-killing missiles but were not aware of the timing or prepared to handle the alarmed reaction of other countries. That makes it all the more important that Beijing explain the purpose of a test whose potential ramifications are immense.

The Bush administration needs to reiterate its often-stated commitment to avoiding an arms race in space and explain how that squares with its statement, just months ago, that "freedom of action in space is as important to the United States as air power and sea power." And there's no better time to do that than now, before China's troubling experiment goads others into responding in kind.