Jan Panteltje wrote in
:

I proposed this before, last year,
the old Russian sonde transmitted only for a very short time...

Don't bet on it. Quicksand is just mud, which is mostly water. If there
was any swampland on Mars, the scientists would have recognized it's
geological structure from orbit. And Mars is pretty cold, so it would be
frozen. If there were fields of dirty ice on the surface of Mars, we'd
probably know it from spectrometry.