Physicists at the University of Twente in the Netherlands experiment the outcomes of landing, by dropping a steel ball onto very fine sand. In addition, the researchers altered the air pressure to observe any potential differences in the landings.
The physicists discovered that by altering the air pressure, they were able to change the height of the sand plume that resulted from the steel ball's landing. This sand plume is similar to a plume that is made when a swimmer cannonballs into a swimming pool; the resulting large splash the swimmer makes, would be similar to the plume of sand from the steel ball.
They found that with lower air pressures, there was a smaller plume of sand, and with higher pressures, the plumes were much larger. This happens because with higher pressures, the air and sand pressures 'mix' in a sort of way, leading to a more fluid like behavior which lessens the friction and causes a higher plume.
On planets with dust such as Mars, this kind of research is the difference between a successful probe landing, and a hundred-million dollar chunk of buried metal.
Original Article: Air Pressure Matters When Landing On Sandy Planets