A massive cloud or plume has been spotted on Mars, and scientists aren't sure what it is or how it got there.
The plume was first spotted by amateur astronomers in March 2012. Wayne Jaeschke, a patent attorney and member of the Association of Lunar and Planetary Observers, said the formation was so unusual he thought something was wrong with his camera.
"I sent a couple of frames to some guys I know in Australia and asked, 'Am I seeing things?'" Jaeschke said, according to National Geographic.
There was nothing wrong with Jaeschke's camera or his eyesight because soon, other amateur Mars-watchers also spotted the formation and saw it grow and change shape for about 10 days. What started out as "double blob protrusions" transformed into a "finger" pointing up into space, according to a study on the formations published in Nature.
Weeks later, a second plume appeared. Like the first, it formed on the planet's "terminator," or the line that divides night from day.
These plumes reached an altitude of 125 to 155 miles, or twice as high as any other plume ever seen on the planet.
“At about 250 km (155 miles), the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,” Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain, lead author of the paper, told the European Space Agency.
Sanchez-Lavega's team came up with two possible explanations, although they don't appear to be particularly happy with either. One is that the plume is a reflective cloud made of particles of water-ice, carbon-dioxide ice or dust. The other is that the cloud is something like an aurora seen here on Earth -- although to be seen from here, it would have to be 1,000 times brighter than any earthly aurora.
The researchers admit that these theories may be flawed.
"Frankly, I'm puzzled by the observations," Bruce Jakosky, an astronomer at the University of Colorado, Boulder and head of NASA's Mars-atmosphere-observing MAVEN mission, told New Scientist. "I don't understand how material can get that high and stay there for so long."