Moon Fountains

When astronauts return to the Moon in the years ahead, they might encounter electrified fountains and other strange things.

It's astounding how prophetic some science fiction has been.

Back in 1956, two years before NASA was even created, Hal Clement wrote a short story called "Dust Rag" published in Astounding Science Fiction, about two astronauts descending into a crater on the Moon to investigate a mysterious haze dimming stars near the lunar horizon. After discarding a wild guess that they were seeing traces of a lunar atmosphere - "gases don't behave that way" - they figured it had to be dust somehow suspended above the ground. In a conversation remarkable for its scientific prescience, one of the astronauts explains:

"…The [Moon's] surface material is one of the lousiest imaginable electrical conductors, so the dust normally on the surface picks up and keeps a charge. And what, dear student, happens to particles carrying like electrical charges?"

"They are repelled from each other."

"Head of the class. And if a hundred-kilometer circle with a rim a couple of [kilometers] high is charged all over, what happens to the dust lying on it?"

The answer, given only by narrative description, is that electrostatic charging caused the dust to levitate.

Well, guess what? Writer Clement was righter than he knew. It appears lunar dust does levitate above the Moon's surface because of electrostatic charging. And the first evidence came almost the way Clement had described.

In the early 1960s before Apollo 11, several early Surveyor spacecraft that soft-landed on the Moon returned photographs showing an unmistakable twilight glow low over the lunar horizon persisting after the sun had set. Moreover, the distant horizon between land and sky did not look razor-sharp, as would have been expected in a vacuum where there was no atmospheric haze.

But most amazing of all, Apollo 17 astronauts orbiting the Moon in 1972 repeatedly saw and sketched what they variously called "bands," "streamers" or "twilight rays" for about 10 seconds before lunar sunrise or lunar sunset. Such rays were also reported by astronauts aboard Apollo 8, 10, and 15.