Comments on the Search for Electrostatic Discharges on Mars

Abstract

Ruf et al. used the Deep Space Network (DSN) to search for the emission of non-thermal radiation by martian dust storms, theoretically predicted by Renno et al. They detected the emission of non-thermal radiation that they were searching for, but were surprised that it contained spectral peaks suggesting modulation at various frequencies and their harmonics. Ruf et al. hypothesized that the emission of non-thermal radiation was caused by electric discharges in a deep convective dust storm, modulated by Schumann resonances (SRs). Anderson et al. used the Allen Telescope Array (ATA) to search for similar emissions. They stated that they found only radio frequency interference (RFI) during their search for non-thermal emission by martian dust storms and implicitly suggested that the signal detected by Ruf et al. was also RFI. However, their search was not conducted during the dust storm season when deep convective storms are most likely to occur. Here, we show that the ubiquitous dust devils and small-scale dust storms that were instead likely present during their observations are too shallow to excite SRs and produce the signals detected by Ruf et al. We also show that the spectral and temporal behavior of the signals detected by Anderson et al. corroborates the idea that they originated from man-made pulse-modulated telecommunication signals rather than martian electric discharges. In contrast, an identical presentation of the signals detected by Ruf et al. demonstrates that they do not resemble man-made signals. The presentation indicates that the DSN signals were consistent with modulation by martian SRs, as originally hypothesized by Ruf et al. We propose that a more comprehensive search for electrostatic discharges be conducted with either the ATA or DSN during a future martian dust storm season to test the hypothesis proposed by Ruf et al.