When mysterious plumes were observed high in the Martian atmosphere by amateur astronomers back in 2012, explanations ranged from massive auroras to a meteor impact. Now it seems that a wild bout of space weather may be to blame for the phenomena.
Clouds on Mars are a
regular occurrence, but the majority form relatively low
in the planet's atmosphere, whereas the freak plumes detected in 2012 were
observed over 250 km (155 miles) above the barren Martian surface.
This altitude puts the plumes in the ionosphere, where the electrically charged solar wind comes into contact with the atmosphere. This suggests that some disturbance of the plasma in the region could be at least partially responsible for the plumes.
No spacecraft were orbiting in a favorable position to directly observe the 2012 phenomenon. However, a wealth of data on Mars' plasma and solar wind environment harvested by ESA's Mars Express spacecraft provided evidence that a significant coronal mass ejection (CME) striking the Martian atmosphere at the correct time and place could account for the plume.
It is theorized that the interference caused by the CME may have stirred up the atmosphere of the Red Planet, causing ionospheric plasma and magnetic fields to buffet high altitude ice dust grains, drawing them into the ionosphere as the plasma escaped into space.
At this point there is not enough evidence conclusively say space weather is a factor in plume creation. There have also been numerous observations of CME emissions striking the Martian ionosphere that did not result in a plume, though this could be the result of unfortunate viewing conditions between Earth and Mars rather than an absence of the features.
If it were discovered that space weather is indeed a factor, the discovery could inform current theories regarding how the Red Planet shed the majority of its atmosphere to space. Planetary scientists believe that Mars once hosted an atmosphere thick enough to maintain liquid water, in an environment that may have once been hospitable to microbial life.