Monday, February 23, 2004

Lava tubes and satellite photography

So, after yesterday's interlude, I will address the problem of how to find lava tubes on the Moon.

There are several techniques available to use. The first one I will consider is satellite photography.

Initially this may seem more than a little silly: how can (visible spectrum) photographs show lava tubes, when they're underground? Fortunately, we can use indirect methods to find lava tubes. If you recall, last Thursday I explained that rima are collapsed lava tubes, and this fact can be used to find intact lava tubes: all you need to do is look for gaps, or more precisely discontinuities, in a visible rille.

A detailed study was done by Coombs and Hawke [1] of imagery from the Apollo missions and the Lunar Orbiter spacecraft, which turned up more than ninety possible lava tubes. An analysis of the data from the 1994 Clementine mission has yet to be carried out [2]. Which brings us neatly to another problem with visible spectrum photography.

The easiest way to pick out rima is by the shadows of their walls - nice dark lines on a light background. Unfortunately, the Clementine mission was geared toward providing good data for geochemical data, and so they arranged to have all its photos taken at local noon - when the shadows are at their least significant. This is a pretty annoying obstacle to using Clementine data to find lava tubes. That and the rather low resolution.

But there are of course ways to look for lava tubes other than satellite photos.


[1] Coombs, C.R., and B.R. Hawke, 'A Search for Intact Lava Tubes on the Moon: Possible Lunar Base Habitats', in The Second Conference on Lunar Bases and Space Activities of the 21st Century (W.W.Mendell, Ed.), NASA CP-3166, Vol. I, p. 219, 1992.

[2] T.L. Billings, 'Lunar Lava Tubes via Clementine',, 17-02-2004


T.L. Billings, Oregon L-5 Society Portland Chapter

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