Plumes Spotted in Martian Atmosphere Baffle Experts

Images of vibrant plumes spotted by amateur astronomers rising to unexpectedly high altitudes in the Martian atmosphere in March and April of 2012 have experts from Europe and the U.S. baffled.

Might they be rapidly developing clouds of frozen carbon dioxide or water ice, dust, or possibly aurora appearing on the morning terminator near the red planet's South Pole?

Plume feature appears in upper right of this image of the Martian disk. Credit W. Jaeschke and ESA.

Similar clouds of ice and dust prospects as well as localized aurora have been observed previously at Mars but never as high as the 200 to 250 kilometer altitudes for the plumes and features observed between March 12-23 and April 6-16 of 2012 by amateur observers and analyzed by an international team of 13 scientists. Nor was solar activity, a stimulus for aurora, unusually high during the periods, according to the science team led by Agustin Sanchez-Lavega of the Universidad del Pais Vasco in Spain.

The team's  assessment is described in Feb. 16 editions of the journal Nature.

The scientists also compare the amateur photographs to a similar feature found in imagery of Mars taken by the Hubble Space Telescope on May 17, 1997 and located by digging into the space observatory's archives.

"At about 250 km, the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,'' says Sanchez-Lavega.

None of the March and April 2012 phenomena were observed by spacecraft orbiting Mars at the time.

"Importantly, both explanations (ice and localized aurora) defy our current understanding of Mars' upper atmosphere," the science team concludes in their Nature publication.

The U.S. MAVEN and Indian Mangalyaan spacecraft maneuvered into Martian orbit last September with new instruments to study the red planet's evolving atmosphere and surface. The European Space Agency's ExoMars Trace Gas Orbiter at the Red Planet mission is expected to launch in 2016 as well.