The vast plume was initially spotted by amateur astronomers in 2012, and appeared twice before vanishing.
Scientists have now analysed the images and say that say the formation, stretching for more than 1,000km, is larger than any seen before.
Writing in the journal Nature, the researchers believe the plume could be a large cloud or an exceptionally bright aurora.
However, they are unsure how these could have formed in the thin upper reaches of the Martian atmosphere.
"It raises more questions than answers," said Antonio Garcia Munoz, a planetary scientist from the European Space Agency.
What's happening at the center of spiral galaxy M106? A swirling disk of stars and gas, M106's appearance is dominated by blue spiral arms and red dust lanes near the nucleus, as shown in the featured image. The core of M106 glows brightly in radio waves and X-rays where twin jets have been found running the length of the galaxy. An unusual central glow makesM106 one of the closest examples of the Seyfert class of galaxies, where vast amounts of glowing gas are thought to be falling into a central massive black hole. M106, also designated NGC4258, is a relatively close 23.5 million light years away, spans 60 thousand light years across, and can be seen with a small telescope towards the constellation of the Hunting Dogs (Canes Venatici).