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"Long before it's in the papers"
February 17, 2015

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Strange cloudy features high over Mars baffle scientists

Feb. 17, 2015
Courtesy of ESA
and World Science staff

Sci­en­tists are re­port­ing that they can’t fig­ure out the cause of mys­te­ri­ous plumes, or cloudy fea­tures, pho­to­graphed high up over Mars by am­a­teur as­tro­no­mers.

Am­a­teurs pro­vid­ed im­ages show­ing the fea­tures on two sep­a­rate oc­ca­sions in March and April 2012, ac­cord­ing to sci­en­tists. The plumes rose to over 250 km (155 miles) over the Red Plan­et’s sur­face, in the same re­gion both times—a height over twice that of any si­m­i­lar fea­tures seen in the past, they added. It’s al­so about 10 times the rec­ord heights for air­plane flight on Earth.

High-altitude plume on Mars. (Courtesy ESA)


The Mar­tian at­mos­phere is almost van­ishin­ly thin at the height of these plumes, which makes them “ex­tremely un­ex­pect­ed,” said Agustin Sanchez-Lavega of the Uni­ver­si­dad del País Vasco in Spain, lead au­thor of a pa­per re­port­ing the re­sults in the jour­nal Na­ture.

The sci­en­tists checked archived Hub­ble Space Tel­e­scope im­ages and am­a­teur im­ages for simi­lar events. These re­vealed oc­ca­sion­al clouds, but usu­ally only up to 100 km high.

The fea­tures in 2012 de­vel­oped in less than 10 hours, sci­en­tists said, of­ten co­vering an ar­ea more than twice as wide as their height, and stayed vis­i­ble for around 10 days, chang­ing from day to day. None of the space­craft around Mars saw the fea­tures be­cause of their po­si­tions and the light­ing con­di­tions.

But one set of Hub­ble im­ages from May 17, 1997, the in­ves­ti­ga­tors said, 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 from am­a­teurs.

Agustin said sci­en­tists have a cou­ple of ide­as so far, but nei­ther seems very like­ly.

“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,” he said.

“An­other idea is that they are re­lat­ed to an au­ro­ral emis­sion,” he said, or light­ing ef­fects caused by the in­ter­ac­tions of so­lar par­t­i­cles with a mag­net­ic field. Sci­en­tists are hop­ing for fur­ther in­sights af­ter the ar­ri­val of a Eu­ro­pe­an Space Agen­cy sat­el­lite at Mars, called the Ex­o­Mars Trace Gas Or­biter. That’s sched­uled for launch next year.


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Scientists are reporting that they can’t figure out the cause of mysterious plumes, or cloudy features, noticed high up over Mars by amateur astronomers. Amateurs provided images showing the features on two separate occasions in March and April 2012, according to scientists. The plumes rose to over 250 km (155 miles) over the Red Planet’s surface, in the same region both times—a height over twice that of any similar features seen in the past, they added. It’s also about 10 times the record heights for airplane flight on Earth. The Martian atmosphere is thin almost to the point of nonexistence at the height of the reported plumes, so they’re “extremely unexpected,” said Agustin Sanchez-Lavega of the Universidad del País Vasco in Spain, lead author of a paper reporting the results in the journal Nature. However, the scientists said, checking archived Hubble Space Telescope images from 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 high. The features in 2012 developed in less than 10 hours, scientists said, often covering an area more than twice as wide as their height, and stayed visible for around 10 days, changing from day to day. None of the spacecraft around Mars saw the features because of their positions and the lighting conditions. But one set of Hubble images from 17 May 1997, the investigators said, 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 from amateurs. Agustin said scientists have a couple of ideas so far, but neither seems very likely. “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,” he said. “Another idea is that they are related to an auroral emission,” he said, or lighting effects caused by the interactions of solar particles with a magnetic field. Scientists are hoping for further insights after the arrival of a European Space Agency satellite at Mars, called the ExoMars Trace Gas Orbiter. That’s scheduled for launch next year.