Extended Data Fig. 8: Test for Poissonian distribution of marsquakes.

Cumulative count of events (left), and lag time distribution (right). For a stationary Poisson process, the cumulative count as function of time should follow a straight line in linear coordinates. The event rate defines the slope of this line. For the first year of operation (cycle 1, blue), we corrected the count after the three weeks down time in August/September 2019 by assuming that the rate during the down time equalled that afterwards. After Sol 400, increasing wind speeds at night made detection impossible until the second Martian year, starting around Sol 700. For the second year (cycle 2), no such correction was necessary. Pale lines indicate the nominal slope (cycle 1: 0.021 ± 0.007 events/sol, cycle 2: 0.053 ± 0.02 events/sol) and the 95% confidence intervals for likely scatter. The event series end with the end of the catalog (MQS v9). The lag times of a stationary Poisson process are exponentially distributed and thus follow a straight line in a semi-logarithmic plot. Lag times shorter than 1 sol were not considered; the daily noise regime makes them unreliable. All confidence were intervals estimated numerically from 1e5 synthetic event sequences with the same rate and covering the same duration.