A massive plume emanating from the surface of Mars remains unexplained after being examined by scientists.
The plume, first noticed by amateur Pennsylvania astronomer Wayne Jaeschke, was observed in March of 2012, and soon confirmed by a number of professional organizations,
USA Today reported.
The plume is the biggest ever recorded on the Red Planet, measuring 155 miles high by up to 600 miles wide on the surface. That means the plume was two times taller than the highest clouds on the planet, and nearly three times bigger than similar plumes recorded by the Hubble Space Telescope.
After being examined by planetary scientists at the European Space Agency, it is still unclear just what the plume was, much less what caused it.
Antonio García Muñoz, one of the scientists who co-authored a report on the plume
published this week in the journal Nature, said that many professional scientists were initially skeptical that the plume was real.
Muñoz called the plumes "exceptional" and "difficult to come to terms with," but said that corroborating images of the plume made it impossible to ignore.
The report speculated that the plume could have been a cloud of ice crystals, however the Martian surface and atmosphere would have to be much colder than usual.
"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," wrote lead author Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain.
A second theory, that the plume was an aurora similar to those observed on Earth, also proved unlikely.
Such a huge aurora would have been 1,000 time stronger than any here on earth, and would have required a large burst of magnetism.
Sanchez-Lavega wrote that such a plume would require "an exceptional influx of energetic particles over days, although solar activity in March 2012 was not unusually high."
Even though the scientists couldn't nail down a surefire theory regarding the origins of the plume, Jaeschke said he's happy to have found "something that stumped the professionals."