Brian / rpage
Static electrical forces could explain part of the clumping and is probably actually a major component of it. Remember the Gusev dust devil animations that seemed to suggest that electrical discharges were part and parcel of dust devil movement? However, I don't think that static electricity would explain the continual clumping after days of drying out and shaking. Clumping which retained the bio-looking appearance of the SODs.
Winston