Planetary Society logo
  • “Exploration is in our nature.” - Carl Sagan

Detecting dust devils

Detecting dust devils
Detecting dust devils The cumulative frequency of transient pressure drops recorded at a fixed station as a function of the size of the drop (divided by the average ambient pressure) from a survey at three field sites near Las Vegas published last year by Peter Lanagan and myself. This fractional pressure drop equates roughly to the square of the circumferential wind speed, with 0.1% being about 10 m/s on Earth or Mars. Note that a small drop can be caused by a direct hit by a small devil, or a near miss of a larger one. The fact that the data from each planet falls roughly on a line on these logarithmic axes suggests that the pressure drops follow a power law, like earthquakes. The field data show that a 0.03% (i.e. 0.3 mbar pressure drop) is seen once per day or two, and that for a given frequency, Mars dust devils are a factor of ~3 more intense in relative pressure terms. Ralph Lorenz