On March 12, 2012, a group of amateur astronomers observed a gigantic plume, visible as a small protrusion, above the surface of Mars. What made this mysterious haze stand out is the fact that though the plume was visible for 11 consecutive days -- from March 12 to March 23 -- scientists have not been able to figure out what gave rise to the formation, which at one point of time, was reportedly spread over a distance of more than 600 miles in the Martian atmosphere.
from International Business Times http://www.ibtimes.com/gigantic-high-altitude-plume-mars-leaves-scientists-puzzled-1818444