Wednesday, May 21, 2008

100 EXPLOSIONS ON THE MOON

May 21, 2008: Not so long ago, anyone claiming to see flashes of light on the Moon would be viewed with deep suspicion by professional astronomers. Such reports were filed under "L" … for lunatic.

Not anymore. Over the past two and a half years, NASA astronomers have observed the Moon flashing at them not just once but one hundred times.

"They're explosions caused by meteoroids hitting the Moon," explains Bill Cooke, head of NASA's Meteoroid Environment Office at the Marshall Space Flight Center (MSFC). "A typical blast is about as powerful as a few hundred pounds of TNT and can be photographed easily using a backyard telescope."

A common question, says Cooke, is "how can something explode on the Moon? There's no oxygen up there."

These explosions don't require oxygen or combustion. Meteoroids hit the moon with tremendous kinetic energy, traveling 30,000 mph or faster. "At that speed, even a pebble can blast a crater several feet wide. The impact heats up rocks and soil on the lunar surface hot enough to glow like molten lava--hence the flash."

During meteor showers such as the Quadrantids or Perseids, when the Moon passes through dense streams of cometary debris, the rate of lunar flashes can go as high as one per hour. Impacts subside when the Moon exits the stream, but curiously the rate never goes to zero.