Scientists baffled by mystery cloud on Mars


The top image shows the location of the mysterious plume on Mars, identified within the yellow circle (south is up), along with different views of the changing plume morphology from images taken by amateur astronomers in 2012.
W. JAESCHKE AND D. PARKER

Scientists are at a loss to explain plumes seen high above the surface of Mars that were observed by amateur astronomers.

“At about 250 km, the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,” says Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain, lead author of the paper reporting the results in the journal Nature.

On two separate occasions in March and April 2012, amateur astronomers reported definite plume-like features developing on the planet.

The plumes were seen on two occasions in March and April 2012 rising above the same region of Mars on both occasions. A check of Hubble Space Telescope archives between 1995 and 1999 showed similar features in the past but only in one recorded case in May 1997 were they higher than 100 km off the planet's surface.

Scientists do not know what causes the effect.

“One idea we’ve discussed is that the features are caused by a reflective cloud of water-ice, carbon dioxide-ice or dust particles, but this would require exceptional deviations from standard atmospheric circulation models to explain cloud formations at such high altitudes,” says Agustin.

“Another idea is that they are related to an auroral emission, and indeed auroras have been previously observed at these locations, linked to a known region on the surface where there is a large anomaly in the crustal magnetic field,” adds Antonio Garcia Munoz, a research fellow at ESA’s ESTEC and co-author of the study.

A plume-like feature was observed on Mars on 17 May 1997 by the Hubble Space Telescope.
JPL/NASA/STScI

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