Two strange, cloud-like plumes reaching high above the surface of Mars are causing a stir among scientists.
On two separate occasions in March and April 2012, amateur astronomers reported definite plume-like features developing on the planet.
The plumes were seen rising to altitudes of over 155 miles (250 km) above the same region of Mars, and could help explain what makes up the Martian atmosphere.
A mysterious plume-like feature, marked with yellow arrow, at the limb of Mars on 20 March 2012.The image is shown with the north pole towards the bottom and the south pole to the top
The phenomenon was observed on March 12, 2012 over the 'terminator', which is the boundary between day and night on Mars.
One of the plumes developed in around 10 hours and lasted for 11 days, shifting shape from 'double blob protrusions' to pillars which merged into a 'finger' shape.
A second was spotted nearby on April 6, 2012, and lasted about 10 days.
'At about 155 miles (250 km), the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,' says Agustin Sanchez-Lavega of the University of the Basque Country in Bilbao, Spain, who led the study.
The phenomenon was observed on March 12, 2012 over the 'terminator', which is the boundary between day and night on Mars. The top images show the location of the mysterious plumes on Mars, identified within the yellow and red circle. The bottom images show different views of the changing plume shape
One of the plumes developed in around 10 hours and lasted for 11 days, shifting shape from 'double blob protrusions' to pillars which merged into a 'finger' shape. Pictured are the 2012 plume events (ringed) on 22 March and 13 April
Their trails were vast, extending between 310 miles and 620 miles (500 and 1,000 km) in north-to-south and east-to-west directions.
The 'clouds' were seen at high altitude, at about 155 miles (250km), roughly above Terra Cimmeria, which is part of Mars' rugged southern highlands, according to the paper.
Mars is being scrutinised for signs of water and volcanic activity, both of which could theoretically nurture some form of life.
Clouds of dust or ice crystals have been spotted occasionally over Mars in the past.
But they have never been as extensive as the latest two, and they always formed at an altitude below 100km.
None of the spacecraft orbiting Mars saw the features because of their viewing geometries and illumination conditions at the time.
However, checking archived Hubble images taken between 1995 and 1999 and of databases of amateur images spanning 2001 to 2014 revealed occasional clouds at the limb of Mars, albeit usually only up to 62 miles (100km) in altitude.
Mars with the plume at limb identified within the yellow circle, and at right, augmented views of the changing plume shape. On the background an area on Terra Cimmeria on Mars where the plume formed
But one set of Hubble images from 17 May 1997 revealed an abnormally high plume, similar to that spotted by the amateur astronomers in 2012.
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 could be made of particles of water or carbon dioxide, said the paper published in the journal Nature Geoscience.
Alternatively, it could be an aurora, similar to the shimmering light show that develops in Earth's atmosphere when solar particles collide with Earth's magnetic field.
Past surveillance by scientific orbiters have suggested Terra Cimmeria to have a 'strip' with a strong but localised magnetic field.
If this is the case, the Martian 'aurora' would be a remarkable 1,000 times brighter than its terrestrial equivalent.
But 'both explanations defy our current understanding of Mars' upper atmosphere', the scientists admit.
The plumes (circled) could be made of particles of water or carbon dioxide. It could be an aurora, similar to the light show that develops in Earth's atmosphere when solar particles collide with Earth's magnetic field
Read more: http://www.dailymail.co.uk/sciencetech/article-2955902/The-mysterious-giant-clouds-spotted-Mars-Scientists-left-baffled-150-mile-high-plumes-coming-red-planet.html#ixzz3TL7epSnc
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