These two views from July 2020 show the elongated cloud stretching from the Arsia Mons volcano on Mars.
ESA / GCP / UPV / EHU Bilbao
This story is part of Welcome to mars, our series exploring the red planet.
The towering Arsia Mons volcano on Mars reaches more than 12 miles (20 kilometers) in height. It’s impressive enough on its own, but it looks wilder when a strange cloud forms over it.
The European Space Agency’s Mars Express spacecraft has been monitoring a “mysteriously long and thin cloud” that appears periodically over Arsia Mons. On Wednesday, ESA took a new look at this cloud based on observations made in July.
“This elongated cloud forms every Martian year during this season around the southern solstice, and repeats for 80 days or even more, following a fast daily cycle,” said Jorge Hernández-Bernal, a doctoral candidate at the University of the Basque Country. in Spain. . “However, we still don’t know if the clouds are always that impressive.”
The cloud can span more than 1,100 miles (1,800 kilometers). Recent observations came around the solstice of southern Mars. “In the early morning hours during this period, this fleeting cloud grows for about three hours, and disappears rapidly a few hours later,” ESA said. Mars Express was in a prime spot to take pictures of the cloud.
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In 2018, when Earthlings observed the cloud, there were some internet speculation indicated new volcanic activity on Mars, But that is not the case. According to NASA, the last Arsia Mons volcanic hurray was about 50 million years ago.
The enigmatic cloud is made up of water ice. The Mars Express science team decided it needed its own name as they continue to investigate its appearances and disappearances. It is now known as the “Arsia Mons Elongated Cloud” or AMEC for short. That is catchy.
