Discussion in 'Science and Technology' started by onedomino, Jun 7, 2005.
After fives weeks stuck in a sand trap:
There must be a lot of silica in the sand on mars, the tracks tend to remain quite faithful to the pattern of the tracs of the vehicle. It is either that or there is more moisture than we are being led to believe.
Electrostatic cohesion? Very fine particles are made cohesive by electrostatic forces between the grains.
Much like on the moon, this would only work if the sand is largely silica. Drive one of these bad boys down pismo beach and see how cohesive the sand is there, you will find that the tracks are not as clear. This was one of the "evidences" of conspiracy that the theorists use to "prove" we never were on the moon, the footprint would not work unless there was either moisture or silicates. Fortunately, we can prove that the sand on the face of the moon is largely made of silicates and that is why the footprint was so well outlined, and the tracks from the rover were so clear.
On Mars, either the sand is largely silicates as well, or there is more moisture in the sand than we are led to believe.
Water and/or silica are not necessary for fine particle cohesion or adhesion: "In dry fine-grained granular media van der Waals forces are the dominating adhesion forces. Under loading the particles are partially deformed irreversibly, such that the effective interface between contacting particles is enlarged by flattening, which leads to enhanced cohesion. This means that the history dependence of cohesion which is due to van der Waals forces arises from plastic deformation of the particles" http://www.ica1.uni-stuttgart.de/Jahresberichte/01/node29.html . For a description of van der Waals forces see this link: http://search.eb.com/nobel/micro/617_56.html .
What are the reports of what is in the sand on Mars? The reason I say that cohesion at this level would necessitate silica is because of the necessity of higher levels of static charge in the sands, silica naturally creates such cohesion. It may be that electrostatic charge builds up higher in the sand because there is little surface liquid to take the charge from the sand, but I still think it more likely that there would be a higher level of silicates in the sand, or more surface moisture than we have been led to believe.
I didn't think I was crazy, the silicates are what causes the bonding in the soil... And salt that binds it together and makes it almost rock. Cool, like the whole salt thing, but that is what caused it not to move when testing, leaving the impression of the tracks would be the silicates' electrostatic charge.
I so love these rovers.....the teams that designed and built them must be so happy......and to think that they got this little guy out of the sand is just outstanding......I love to think about all the stuff that we are learning from their adventures. Spirit and Opportunity are providing us an alternative to some of our lesser endeavors here, on our third rock from the sun.
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