'Cloud' over Mars leaves scientists baffled

Phys dot Org ^ | February 16, 2015 | unattributed

[SunkenCiv]

Plumes seen reaching high above the surface of Mars are causing a stir among scientists studying the atmosphere on the Red Planet.

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 250 km above the same region of Mars on both occasions. By comparison, similar features seen in the past have not exceeded 100 km.

"At about 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 Universidad del País Vasco in Spain, lead author of the paper reporting the results in the journal Nature.

The features developed in less than 10 hours, covering an area of up to 1000 x 500 km, and remained visible for around 10 days, changing their structure from day to day.

None of the spacecraft orbiting Mars saw the features because of their viewing geometries and illumination conditions at the time.

However, checking archived Hubble Space Telescope 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 100 km in altitude.

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.

[gleeaikin]

The source I first saw on this subject said this haze was also seen about a year previously. If it was in the same area, then I think that rules out an impact event.

[gleeaikin]

I forgot to include this article also on the mars story.

http://www.aol.com/article/2015/02/17/scientists-baffled-by-mysterious-haze-on-mars/21143468/?ncid=webmail11

[SunkenCiv]

Thanks g. None of the sources I've been able to read (the Nature source might be nice, but it requires authorization) say that there have been multiple events in the same spot -- merely that two amateurs saw a similar phenomenon twice (well, three times) in 2012. Here's the snip from the BBC piece linked out of that AOL piece.

The vast plume was initially spotted by amateur astronomers in 2012, and appeared twice before vanishing. Scientists have now analysed the images and say that the formation, stretching for more than 1,000km, is larger than any seen before. The vast, bright haze lasted for about 10 days. A month later, it reappeared for the same length of time. But it has not been seen since.

[SunkenCiv]

No prob’. It’s interesting that the science-critter gets quoted in some sources that these plumes shouldn’t be seen at such high altitudes, that it would mean the Earthlings’ understanding of the atmosphere of Mars is incorrect (due to the low density). Obviously it *has* to be either from an impact, or from a volcano, but again, the latter would mean current volcanic activity, and the most recent known was about 2 million years ago. :’)