A mysterious elongated cloud has reappeared over Arsia Mons, a Martian volcano that is 20 kilometers high, and is being accompanied by the Mars Express – orbiter of the European Space Agency. It may seem new, but the phenomenon was first detected in 2009, and the images revealed this week show that it remains firm and strong – even if it is not constant.
Contrary to what most anxious people might think, it does not seem to be linked to any volcanic activity, since the last time Arsia was active was about 50 million years ago, according to NASA. The suspicion, in this case, is that the cloud is composed of ice and water, flowing down the sloping sides of the mountain in question.
The records were captured on July 17 and 19 by the equipment’s visual monitoring camera and suggest that it is 1,800 km long, varying according to the time of year. For example, during the solstice in the southern hemisphere of Mars, equivalent to December 21 on Earth, the cloud grows for a few hours a day and disappears shortly thereafter.
Jorge Hernandez-Bernal, lead author of an ongoing study on the phenomenon, says: “It is formed every year during this season and is repeated for 80 days or more, following a fast daily cycle. However, we still do not know if the clouds are always so impressive “.