Saturday, February 7, 2009

Hal Clement's "Dust Rag" (short story, lunar atmosphere)

An illustration accompanying the 2005 NASA paper titled Moon Fountains that compares observed properties and current theories of lunar atmosphere vis-a-vis those suggested by the 1956 short story titled Dust Rag by Hal ClementThis may be among the most important hard sf stories by anyone. Unfortunately, it doesn't appear to be among the widely read ones.

Story describes the phenomenon of lunar haze - a thin constantly renewed atmosphere of dust on moon. What constantly kicks up this dust? Why doesn't it immediately fall down rather than remain suspended? A 2005 NASA paper discusses this story vis-a-vis actual observed phenomenon & currently accepted theories.

Story also has some things to say on the design of space suites.

Plot is classic Clement: a couple of men get into a life & death situation. Only reasoning based on elementary physics or chemistry (in this case, physics) will get them out of jam.

An aside: This story made me see a plot pattern that seems to be common across many Clement stories, & which appears to be the same as one in ancient Sanskrit story of "Enchanted Pool" in Mahabharata. More on it in a separate post.

Story summary.

Ridging & Shandara are two from a research station on moon - it's still early days of lunar exploration. Expedition had discovered a local magnetic field; "the south magnetic pole - or a south magnetic pole - lay a few hundred miles away." Duo are going there to set up some instruments.

The pole lies on the a peak at the rim of something called Pluto crater. Previous telescopic observations from earth had observed periodic obscuring of its surface that lasts varying lengths of time. They make a trek into crater see if they can find anything.

They're puzzled by what is obviously a local atmosphere! They rule out presence of gases for reasons I didn't catch. So it must be super-fine dust. What could be causing its ejection, & what could be keeping it suspended?

Life & death situation happens when they instinctively wipe their transparent space suit plastic in front of their eyes, as the vision begins getting unexpectedly blurred by haze. Only, the wiping with space suit sleeve seems to stick the dust to surface in front of their eyes rather than remove it! They are quickly blinded. And no hope of rescue: "there isn't enough fuel on the Moon to get a rescue tractor out here, even if anyone knew we were in trouble & could make the trip in time."

One will eventually reason the atmosphere & why wiping is not helping.

"we have reason to believe there's a magnetic storm going on, which strongly suggests charged particles from the Sun. We are standing, for practical purposes, on the Moon's south magnetic pole." "There are, at a guess, protons coming from the sun. They are reaching the Moon's surface here - virtually all of them, since the Moon has a magnetic field but no atmosphere. The surface material is one of the lousiest imaginable electrical conductors, so the dust normally on the surface picks up & keeps charge. And what, dear student, happens to particles carrying like electrical charges?"

"They are repelled from each other."

"And if a hundred-kilometer circle with a rim a couple of kilos high is charged all over, what happens to the dust lying on it?"

That's the reason for dust atmosphere, also favored by NASA now: moondust electrically charged because of interaction with solar wind levitates.

But why cannot they wipe their faceplates? "Whenever two materials rub against each other, electrons come loose... Unless the materials are of identical electronic makeup, which for practical purposes means unless they are the same substance, one of them will hang onto the electrons a little - or a lot - better than the other, so one will have a negative net charge & the other a positive one. It's our misfortune that the difference between the plastic in our faceplates & that in the rest of the suits is the wrong way; when we rubbed the two, the faceplates picked up a charge opposite to that of the surrounding dust - probably negative, since I suppose the dust is positive & a transparent material should have a good grip on its electrons."

They'll try several things, none very helpful. Eventually, what saves them is the rubbing of their faceplates against each other. One of the two will lose dust ("one of them was bound to go positive") & gain vision, & lead the way out of haze.

Fact sheet.

First published: Astounding Science Fiction, September 1956.
Rating: A.
Listed among the stories from John Campbell's Astounding/Analog.


  1. Stories of Hal Clement.
  2. Stories from Astounding/Analog.
  3. Arthur Clarke's novel "A Fall of Moondust": Far more widely read than this Clement story. But according to this NASA paper, Clarke's description of moondust is wrong & Clement's is right.


Rich said...

I just did a quick Google search for "blospot+Hal+Clement" and I am glad I did. I will keep this story in mind, now. Even considering the inherent personal bias in book recommendations, I already know I like Clemet as an author.

Is this short story included in any anthologies or collections that you could point out?

Tinkoo said...

I think it's in the "Best of Hal Clement".