First direct evidence of lightning on Mars

BY DR EMILY BALDWIN

ASTRONOMY NOW

Posted: 23 June, 2009

University of Michigan researchers say they have found direct evidence for lightning on Mars caused by a large dust storm.

"What we saw on Mars was a series of huge and sudden electrical discharges caused by a large dust storm," says Chris Ruf from the departments of Atmospheric, Oceanic and Space Sciences and Electrical Engineering and Computer Sciences. "Clearly, there was no rain associated with the electrical discharges on Mars. However, the implied possibilities are exciting."

The findings were made using an innovative microwave detector developed at the University of Michigan Space Physics Research Laboratory. The kurtosis detector is capable of differentiating between thermal and non-thermal radiation, where non-thermal radiation is associated with the presence of lightning. Between 22 May and 16 June 2006 the instrument took measurements of microwave emissions for approximately five hours each day, and on 8 June both an unusual pattern of non-thermal radiation and an intense Martian dust storm occurred, the only time that non-thermal radiation was detected.

An illustration of a dust storm on Mars. New research suggests that intense dust storms could create electrical discharges. Image: Brian Grimm and Nilton Renno.

After reviewing the strength, duration and frequency of the non-thermal activity, as well as the possibility of other sources, the scientists arrived at the conclusion that the dust storm most likely caused dry lightning. The work confirms soil measurements from the Viking landers 30 years ago that suggested that dust storms might be electrically active like Earth’s thunderstorms and therefore might be a source of reactive chemistry, but at the time the theory was untestable.

In 2006, theoretical modelling, laboratory experiments and field studies on Earth led to the conclusion that there was no direct evidence that lightning occurred on Mars. The new research clearly challenges those findings and has significant implications for Mars science.

"It affects atmospheric chemistry, habitability and preparations for human exploration. It might even have implications for the origin of life, as suggested by experiments in the 1950s," says Nilton Renno, a professor in the Department of Atmospheric, Oceanic and Space Sciences.

"Mars continues to amaze us," adds Michael Sanders of the Jet Propulsion Laboratory. "Every new look at the planet gives us new insights."

The new findings will be published in a forthcoming issue of Geophysical Research Letters.