The European Space Agency said this week (February 16, 2015) that scientists are scratching their heads over mystery plumes seen reaching high above the surface of the Red Planet, Mars. Amateur astronomers were the first to report plume-like features developing on Mars, on two separate occasions in March and April 2012. A check of Hubble images also revealed an abnormally high plume in May, 1997, similar to those spotted by the amateurs. Scientists are now working on determining the nature and cause of the plumes by using the Hubble data in combination with the images taken by amateurs.
The plumes have been seen rising to altitudes of over 150 miles (250 km) above the same region of Mars on both occasions. By comparison, similar features seen in the past have not exceeded about 60 miles (100 km). Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain, lead author of a paper reporting the results in the journal Nature, said:
At about 250 km, the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected.
The features were seen to develop in less than 10 hours. They cover an area of about 600 x 300 miles (1000 x 500 km) have been seen to remain visible for around 10 days. Day by day, the strange plumes change shape.
Why didn’t our spacecraft see them? ESA says none of the spacecraft orbiting Mars saw the features because of their viewing geometries and illumination conditions at the time.
At this point, scientists studying the atmosphere of Mars are unsure what they are. Agustin said:
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.
Antonio Garcia Munoz, a research fellow at ESA’s ESTEC and co-author of the study, added:
Another idea is that they are related to an auroral emission, and indeed auroras have been previously observed at these locations, linked to a known region on the surface where there is a large anomaly in the crustal magnetic field.
ESA says further insights into the mysterious Martian plumes should become possible following the arrival of ESA’s ExoMars Trace Gas Orbiter at the Red Planet, scheduled for launch in 2016.