Mysterious 'Cloud' Over Mars Baffles Scientists

The location of the mysterious plume on Mars is identified within the yellow circle along with different views of the changing plume morphology taken by W. Jaeschke and D. Parker on 21 March 21 2012. W. Jaeschke and D. Parker/European Space Agency

Scientists have been left confused as to what an "extremely high-altitude plume" seen emanating over Mars could be.

First spotted in March 2012 by amateur astronomers, the plume appeared for 10 days, disappeared, and was then seen again for 10 days in April the same year. Planetary scientists have now analysed the haze, and this week published a paper with their findings.

"The Martian limb (that is, the observed 'edge' of the planet) represents a unique window into the complex atmospheric phenomena occurring there", begins the paper which was published in the journal Nature. However, in terms of explaining what the plume could be, scientists are somewhat stumped.

Dr Antonio Garcia Munoz, a planetary scientist at the European Space Agency and one of the authors of the paper says his team haven't come to any firm conclusions as to what the plume could be but speculated two options: it could be a cloud, or an aurora borealis.

The paper says clouds of ice-crystals are known to exist in the Martian atmosphere but not above 100 km, and that if it is an aurora borealis it is "of a brightness more than 1,000 times that of Earth's aurora, over a region….where aurorae have previously been detected."

Dr Munoz says: "Each of them have pros and cons, but it's still difficult to explain the phenomenon with those explanations."

Without the work of amateur astronomers says Dr Munoz, there would not have been such a discovery. "It was critical. We don't have any additional data from any space mission or ground telescopes. Things are getting better in that there's better communication between the amateur community and the professional community."

"Now we have to pay close attention to see if similar events happen in the near future. There are many questions still to be answered, questions we couldn't even imagine. In a way we have to be humble, there are many things to find out."

The European Space Agency say further insight into the phenomenon could be possible when their ExoMars Trace Orbiter - scheduled for launch in 2016 - reaches the Red Planet.