Mile-Long Mystery Cloud Over Martian Volcano May Yield Its Secret After Decades

ARSIA MONS, MARS — A cloud stretching more than 900 miles across the surface of Mars, first photographed in the era of NASA's Viking missions, may at last be giving up its secrets, according to a report published by The Debrief.

The report states that Viking 2 reached the planet in late 1976 and, over the following two years, returned thousands of images. Among them was a vast formation unlike anything scientists had previously seen on the Red Planet. It is now known as the Arsia Mons Elongated Cloud, or AMEC, after the great volcano above which it appears.

According to the account, the cloud is typically seen in the Martian spring and summer and is most prominent in the morning. It is made chiefly of water ice crystals, which warm seasonal winds are said to carry over long distances. NASA and international partners, including the European Space Agency and its Mars Express spacecraft, have studied it for decades.

The difficulty, the article explains, lies in how such a cloud could form at all. On Earth, water vapor condenses or freezes onto microscopic airborne particles such as dust. The Martian atmosphere is extremely thin, and at the altitudes where the cloud forms there may not be enough dust to do the same job.

Based on recent research, scientists now believe the cloud may arise from a process that does not depend on dust particles. If correct, the report says, this could reveal previously unrecognized aspects of cloud formation in planetary atmospheres, and future observations of thin atmospheres elsewhere might offer confirmation.

The author adds that solving the puzzle could help refine understanding of atmospheric processes on Mars and, potentially, on Earth as well.