>Therefore it is difficult to say whether the foot pads would have been covered in dust with any certainty.<


Concerning the reasons why there is no dust on the lem's landing pads earlier in the thread, I have formulated a pet (half baked) theory which I'd like to put up on offer.
In some of the better photographs you can discern on the inner faces of each of the pads where it is adjacent to the engine exhaust bell, it appears to be covered with a different coloured material to the outer edges which are covered in the gold coloured Mylar. The material is similar in colour to the engine's exhaust bell. Dark grey/black. It is fairly clear on
http://www.hq.nasa.gov/office/pao/Hi...11-44-6574.jpg
LLL
http://www.hq.nasa.gov/office/pao/Hi...11-40-5917.jpg
or http://www.hq.nasa.gov/office/pao/Hi...11-40-5920.jpg

This suggests to me that the designers were providing some form of protection from the heat of the exhaust efflux. Therefore it seems to me likely, that they expected the possibility that the exhaust gasses would diffuse downwards and sideways sufficiently to partly impinge on the pad.
Common sense expectation tells me that if the exhaust is directed downwards it would not be likely to come anywhere near the pads which are well outboard of the exhaust nozzle. But consider the film of any Saturn launch when it reaches high altitude and is above the Earth's atmosphere. It can be seen that its exhaust appears to extend well above the level of the exhaust nozzles and 'creeps' up the side of the stage. This, I understand, is because it is exhausting into a vacuum, and it is occurring on a vehicle travelling forwards at several thousand mph. During the descent phase of the landing the lem is travelling backwards into its own exhaust at relatively low speed and would be descending into a dissipating zone of pressure, especially in the last moments before touchdown.
If that were so, then the pad would be swept clear of any displaced dust as it travelled backwards into its own exhaust until the engine cut off some three feet (plus) above the surface. By the time the pad touched down any dust displaced by the exhaust would have long since departed on a flat, sideways trajectory and therefor, in a vacuum there would be no possibility of dust coming anywhere near the pads, much less settle on them.
No doubt others who are more familiar with lem and engine design will find the holes in this theory that probably exist but it seems to me to be an aspect that I haven't seen considered before.
DK

edit: added photo reference

<font size=-1>[ This Message was edited by: Dave Kew on 2002-11-04 18:47 ]</font>