Chuck Bednar for redOrbit.com – @BednarChuck
Cloud-like plumes spotted rising high above the surface of Mars on two separate occasions have scientists scratching their heads.
According to the ESA, the plume-like features were reported by amateur astronomers in March and April 2012. They were seen rising to altitudes of more than 155 miles (250 kilometers) over the same region of Mars on each occasion.
The features developed in under 10 hours and covered an area of up to 620 miles by 310 miles (1000 kilometers by 500 kilometers) and remained visible for about 10 days, changing their structures on a daily basis.
Similar plume-like structures observed in the past never exceeded 62 miles (100 kilometers) in size, and the two larger ones were not detected by any of the spacecraft orbiting Mars because of their viewing geometries and illumination conditions at the time, the ESA said.
“At about 250 km, the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,” explained Agustin Sanchez-Lavega, a professor at Spain’s Universidad del País Vasco and the lead author of a paper on the unusual plumes, which has been published in the journal Nature.
ESA planetary scientist Antonio García Muñoz told USA Today that he and his colleagues were skeptical of the reports at first, but as they looked into the matter, they ultimately “came to the conclusion that what we were seeing is actually real.” He called the plumes “exceptional” and added that he was finding it “difficult to come to terms with” the discovery.
Go to the databases!
The researchers checked an archive of images taken by the Hubble Space Telescope from 1995 to 1999, as well as databases of amateur photographs captured between 2001 and 2014. In most cases, they found occasional plumes up to 100 kilometers in size, but one set of Hubble images from May 17, 1997 showed an abnormally high plume similar to the ones reported in 2012.
Damian Peach, one of the first astronomers to detect the phenomenon, told the BBC News that he had noticed a “projection sticking out of the side of the planet.” At first, he said he thought there was some kind of issue with his camera or telescope, “but as I checked more of the images, I realized it was a real feature – and it was quite a surprise.”
The cloud-like haze remained for roughly 10 days in March, reappeared for about the same amount of time a month later, and since disappeared, the British news agency added. Now, scientists are working to determine the exact nature and the cause of these plumes by using a combination of Hubble data and information obtained by citizen scientists like Peach.
“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,” Agustin said.
“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,” added García Muñoz.
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