The Allen Telescope Array Search for Electrostatic Discharges on Mars

TL;DR

This study used the Allen Telescope Array to search for electrostatic discharges on Mars by analyzing radio emissions, but found no evidence of lightning, instead detecting RFI signals with similar spectral features.

Contribution

Developed a wideband spectrometer for detecting non-Gaussian radio signals from Mars, applying spectral kurtosis analysis to search for electrostatic discharges.

Findings

No signals indicating lightning discharge were detected.

Detected RFI signals with spectral peaks at 10 Hz harmonics.

Dust storms did not produce observable electrostatic discharges.

Abstract

The Allen Telescope Array was used to monitor Mars between 9 March and 2 June 2010, over a total of approximately 30 hours, for radio emission indicative of electrostatic discharge. The search was motivated by the report from Ruf et al. (2009) of the detection of non-thermal microwave radiation from Mars characterized by peaks in the power spectrum of the kurtosis, or kurtstrum, at 10 Hz, coinciding with a large dust storm event on 8 June 2006. For these observations, we developed a wideband signal processor at the Center for Astronomy Signal Processing and Electronics Research (CASPER). This 1024-channel spectrometer calculates the accumulated power and power-squared, from which the spectral kurtosis is calculated post-observation. Variations in the kurtosis are indicative of non-Gaussianity in the signal, which can be used to detect variable cosmic signals as well as radio frequency interference (RFI). During the three month period of observations, dust activity occurred on Mars in the form of small-scale dust storms, however no signals indicating lightning discharge were detected. Frequent signals in the kurtstrum that contain spectral peaks with an approximate 10 Hz fundamental were seen at both 3.2 and 8.0 GHz, but were the result of narrowband RFI with harmonics spread over a broad frequency range.