Emission of non‐thermal microwave radiation by a Martian dust storm

Abstract

We report evidence for the emission of non‐thermal microwave radiation by a deep Martian dust storm. The observations were made using an innovative detector that can discriminate between radiation of thermal and non‐thermal origin by measuring the high order moments of its electric field strength. Measurements with this detector, installed in a 34 m radio telescope of the Deep Space Network (DSN), were made for about 5 hours a day over a dozen days between 22 May and 16 June 2006. Non‐thermal radiation was detected for a few hours only when a 35 km deep Martian dust storm was within the field of view of the radio telescope on 8 June 2006. The spectrum of the non‐thermal radiation has significant peaks around predicted values of the lowest three modes of the Martian Schumann Resonance (SR). The SR results from electromagnetic standing waves formed in the concentric spherical cavity between the Martian surface and its ionosphere and forced by large‐scale electric discharge. Thus, the non‐thermal radiation was probably caused by electric discharge in the Martian dust storm.

Non‐detection of impulsive radio signals from lightning in Martian dust storms using the radar receiver on the Mars Express spacecraft

“…Other smaller isolated storms have also been investigated. One such case is the dust storm for which Ruf et al [2009] reported evidence of electrostatic discharges from 19:14 to 22:40 UT on June 8, 2006. MOC images show that this dust storm was active from June 6 to 8.…”

“…However, because of the much lower atmospheric pressures at Mars and the corresponding lower breakdown threshold, ∼20 to 30 kV/m, it has been suggested that electrostatic charging in Martian dust storms could cause lightning-like electrical discharges [Eden and Vonnegut, 1973;Sentman, 1991;Melnik and Parrot, 1998;Farrell et al, 1999;Zarka et al, 2004;Renno and Kok, 2008]. Recently, Ruf et al [2009] reported periodic fluctuations in the non-thermal microwave emission from a Martian dust storm that they attribute to the excitation of Schumann [1952] resonances by electrical discharges. In this paper we report the results of a search for impulsive HF (highfrequency) radio signals from lightning in Martian dust storms using the radar receiver on the Mars Express spacecraft.…”

Applications of Electrified Dust and Dust Devil Electrodynamics to Martian Atmospheric Electricity

“…In terms of arguments against Martian atmospheric electricity, Ruf et al (2009) reported the possible remote-sensed detection of lightning emission at 8 GHz from Mars using a terrestrial-based radio telescope. Given the detection, the electric dipole moment to account for the discharge was found to be relatively large.…”

An improved parameterization of wind‐blown sand flux on Mars that includes the effect of hysteresis

“…Moreover, electric fields generated in saltation and dust storms [Kok and Renno, 2008] could affect atmospheric chemistry [Kok and Renno, 2009a] and produce electric discharges [Ruf et al, 2009].…”