Could lightning occur on Mars?

Martian lightning Artist’s impression of an electrical discharge on Mars. (Courtesy: Milan Machatý, Faculty of Mathematics and Physics, Charles University and Institute of Atmospheric Physics, Czech Academy of Sciences) Researchers in the Czech Republic say they may have observed the signature of a “whistler” in a one-second snapshot captured by the MAVEN probe orbiting Mars. The event, observed in the ionosphere of the planet, would be the first lightning-like electric discharge activity ever to be seen there and the finding will be important for understanding atmospheric processes in the Martian atmosphere. “Whistlers are well known on Earth and are associated with lightning,” explains space physicist František Němec at Charles University , who led this research effort. “Our result implies that this phenomenon also occurs on our planetary neighbour.” Unlike Earth, Mars does not have a global magnetic field, but only localized fields created by magnetized materials in the planet’s crust. And because its atmosphere is thin, lightning on this planet does not originate in water clouds but instead in dust storms, similar to those observed in volcanic eruptions here on Earth, and in dust devils. During dust storms, dust grains become electrically charged as they collide with each other and generate an electric field. On Mars, previous studies have predicted that this field can discharge when its value exceeds the breakdown threshold in the low-pressure Martian atmosphere, which is around 15 kV/m . Dust devils, for their part, can produce ultralow-frequency radiation on Earth thanks to the electrical charges that fluctuate as the dust swirls around. Since both dust devils and dust storms are much stronger on Mars, theory suggests that they could generate wideband radiation that we could detect on Earth . Despite recent measurements by the Allen Telescope Array , the Mars Global Surveyor (MGS) and Mars Atmosphere and Volatile Evolution (MAVEN) missions and the Mars Express spacecraft , conclusive evidence for Martian lightning has yet to be found. Analysing electromagnetic radiation Another way to detect these electric discharges, says Němec, is to analyse the electromagnetic radiation that accompanies them. This radiation lies in the extremely low frequency/very low frequency range and, under some conditions, can reach the ionosphere of a planet. The phenomenon was first identified and observed on Earth shortly before the space era and such electromagnetic waves have successfully been used to provide evidence for lightning on Jupiter , Saturn and Neptune since then. These waves are known as whistlers, he explains , because of their characteristic spectral pattern in the plasma medium of the ionosphere. Here, higher frequency waves propagate faster and arrive at the observation point sooner than lower frequency ones, resulting in a characteristic “whistling” spectral shape. The observational challenge is that these waves can penetrate the Martian ionos