Mars is one of the most well-studied objects in the solar system. Incredibly, the first map of its surface appeared five hundred years ago, when astronomers distinguished the dark spot of the Great Sirte plateau and the bright polar ice caps of the Red Planet. Subsequently, a whole army of semi-autonomous vehicles took up the exploration of Mars, seven of which are still collecting data.
The atmospheric phenomena of the Red Planet have always been in the center of attention of scientists. With the help of various spacecraft and ground-based telescopes, scientists have observed and are observing numerous dust storms, vortices, plumes, clouds of ice crystals and aurora on Mars.
But when on March 12, 2012, amateur astronomers noticed a strange formation on Mars, which was located at an altitude of 250 kilometers above the southern hemisphere, it caused complete bewilderment in the scientific community. The fact is that earlier phenomena similar in structure were observed at a maximum of 100 kilometers.
A new "cloud" in the form of a giant drop persisted for eleven days, constantly changing its shape. During this time, the formation has reached a diameter of one thousand kilometers and stretched out towards space. Unfortunately, the deteriorated weather did not allow tracing the further fate of the formation, and when the clouds on the Earth parted a week later, it had already disappeared.
The controversy surrounding the nature of the mysterious phenomenon was in full swing when on April 2 of the same year it arose again at the same point on the planet. For various reasons, both events did not hit the camera lenses of spacecraft operating in orbit and on the surface of Mars.
To unravel the nature of the atmospheric “outgrowths”, a team from the University of the Basque Country (Universidad del País Vasco), led by Agustin Sánchez-Lavega, carefully examined the archive of photographs of Mars. They were obtained by the Hubble telescope from 1995 to 1999. Scientists also inspected a database of amateur images for the period from 2001 to 2014.
As a result, only on a single series of images of the Hubble telescope from March 17, 1997, the researchers found a high plume, similar to the one observed in 2012. The researchers expressed their first conclusions and assumptions in an article that was published in the publication Nature.
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Snapshot with the same "cloud" from 1997
The simplest explanation for ultra-high formations could be dust storms, which are not uncommon on the Red Planet. But in the entire history of observations, they have never exceeded 50 kilometers. Extremely unusual weather conditions would be necessary to reach 250 kilometers, which does not fit all existing models of the atmospheric circulation of Mars.
Researchers consider the involvement of fragments of frozen water vapor and carbon dioxide in the described phenomenon much more realistic. But in this case, one has to assume that the temperature of the Martian atmosphere is much lower than was previously assumed.
Dust storm plumes on Mars usually don't rise above 50 kilometers (NASA photo).
"The observed formations can also be associated with auroras," study co-author Antonio Garcia Munoz said in a press release from the European Space Agency. "Indeed, auroras that are associated with areas of severe magnetic anomalies have been observed in the same area of the planet before."
Work on the analysis of unusual atmospheric phenomena on Mars continues to this day. Scientists also hope that they will be able to better understand the issue after the delivery to the Red Planet of the Martian scientific orbiter TGO, which is scheduled to launch in 2016.
Note that the "cloud" is far from the only mystery of Mars. Not so long ago, astronomers looking for traces of possible ancient life on the Red Planet were puzzled by the periodic emissions of methane that the Curiosity spacecraft recorded.
