Martian plumes remain a mystery

New Scientist : Other than Earth, Mars is the most studied planet in the solar system. Nevertheless, mysterious phenomena continue to be observed there. On 12 March 2012 amateur astronomers saw what appeared to be a plume of gas and dust rising up to 250 km above Mars’s surface. Over the next 11 days the plume grew to cover an area 1000 km across. By 2 April it had faded away. Just 4 days later a second plume appeared that lasted another 10 days. To date, no one has provided a satisfactory explanation of the plumes’ origin. Agustin Sánchez-Lavega of the University of the Basque Country, Spain, and his colleagues have collected images of those events and searched archival images of Mars. Among the images, the researchers found a similar event from 1997. Because of the plumes’ altitude and duration, they are unlike any other known clouds in the solar system. And as there are no known active volcanoes on Mars, they probably aren’t volcanic plumes. Observing another such event may be the best option for figuring out what is going on, but they occur so rarely that it could be some time before that’s possible.