One of the most studied planets in our solar system has a new mystery. Giant plume features spotted two separate times on Mars’ limb. Once in March 2012, and a second a month later. Each plume rose more than 250 kilometers above the surface in the same area.
According to an ESA press release, similar plumes have been seen in the past – but none rose past 100 kilometers.
“At about 250 km, the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,” said Agustin Sanchez-Lavega, lead author of the paper published in Nature.
The plumes developed extremely fast. Inside of 10 hours, the plumes covered an area up to 1000 x 500 km. They remained visible for nearly 10 days and observations showed their structure changing every day.
The plumes were discovered by amateur astronomers. But, what about all the satellites orbiting the red planet? None of them were able to spot the plumes due to their viewing orbits and illumination conditions at the time.
After the discovery, scientists went back and looked at images taken by the Hubble between 1995 and 1999. They found several instances of plumes at up to 100 km. One image taken on May 17, 1997 did show a plume similar to the one seen in 2012 by amateur astronomers.
What Could the Plumes Be?
Scientists don’t have a definitive answer, but they do have a couple of theories.
“One idea we’ve discussed is that the features are caused by a reflective cloud of water-ice, carbon dioxide-ice or dust particles, but this would require exceptional deviations from standard atmospheric circulation models to explain cloud formations at such high altitudes,” says Agustin.
Co-author Antonio Garcia Munoz says it could also be “related to an auroral emission.” He says auroras have been spotted in the that area before. The scientists cite a strong magnetic anomaly in the area that could create an aurora that shines 1,000 times brighter than those seen above Earth.
Whatever the reason, “both explanations defy our current understanding of Mars’ upper atmosphere,” the scientists write in their paper.
The ESA hopes their ExoMars Trace Gas Orbiter will be able to shed some light on this phenomenon. It is expected to enter orbit around Mars in 2016.
One of the orbiter’s main goal will be taking a closer look at methane and other gases that are present in Mars’ atmosphere in small concentrations. You can read more about the orbiter’s mission here including the Entry, Descent and Landing Demonstrator Module (EDM) that will be tested.
Image credits: NASA, ESA