Only thanks to a camera on board ESA’s Mars Express orbiter, which was not designed for this purpose at all, a group of researchers has found out what an unusual and huge cloud on Mars is all about. It appears regularly in the early morning beyond the field of view of most instruments at a huge shield volcano, is pulled in a few hours with rough speed into the long and then dissolves. Only with the help of the on-board surveillance camera of Mars Express it was first discovered and now investigated.
Always in the morning
As the scientists now explain in the Journal of Geophysical Research, they have determined that the giant cloud forms every morning shortly before sunrise in the spring and summer on Mars. It is therefore an "orographically excited" cloud, which is formed when wind is printed upwards on the slopes of the Arsia Mons volcano. For two and a half hours, the cloud is then pulled westward at over 600 kilometers per hour and reaches a height of 45 kilometers. In the process, it will be nearly 2000 kilometers long and 150 kilometers wide, according to the report. In the late morning, it breaks away from the volcano and disappears in the face of rising temperatures.