This figure shows the signature of a dust devil that passed over the Pathfinder Lander on Sol 25. Since then we have seen several similar features. The black line shows surface pressure plotted over a period of approximately two minutes. The sharp minimum approximately 0.5% below the background pressure is very clear. The dashed curves show raw data from two hot wire wind sensor elements (Blue = Wind Sensor 4 = East Wind, Red = Wind Sensor 1 = West Wind). When the wind blows directly on an element it cools. It is clear from the figure that the East wind increases suddenly as the dust devil approaches the lander and the pressure begins to fall. As the dust devil passes over the lander, pressure begins to rise, the East wind dies away and the West wind increases suddenly. Finally as the dust devil moves away, pressure returns to normal and the West wind dies away. This is a textbook dust-devil signature.
Photojournal note: Sojourner spent 83 days of a planned seven-day mission exploring the Martian terrain, acquiring images, and taking chemical, atmospheric and other measurements. The final data transmission received from Pathfinder was at 10:23 UTC on September 27, 1997. Although mission managers tried to restore full communications during the following five months, the successful mission was terminated on March 10, 1998.