A longer cloud passes over California mars‘red cheek. Apparently, an impressionist artist filled his palette knife with white and drew a line across the canvas to where the oil paint would go.
That’s not what astrophysicist Jorge Hernández Bernal saw for the first time during Mars Express in 2018. Visual Surveillance Camera(Opens in a new window) — Affectionately known by the European Space Agency Mars webcam(Opens in a new window) – posted a new photo. About 20 years ago, with the average resolution of a standard computer camera, it was elegant and unintelligible. But Bernal, who studied Martian meteorology at the University of the Basque Country in Spain, immediately recognized the shadow as something else: a mysterious weather event on the Red Planet.
It wasn’t until researchers could look at the cloud with better equipment that it revealed the Martian cloud in all its vast glory. The team delved deeper into the photo archives and discovered that it was often there. He was there through all the difficulties and even during it NASAof Viking 2 mission(Opens in a new window) In the 1970s.

The low-resolution camera on the European Space Agency’s Mars Express probe captured the giant cloud for the first time in 2018.
Credit: ESA
The secret was knowing when to look for it.
“There were people who thought ESA was faking it,” Bernal told Mashable. “It was a bit difficult because I was really young at the time [of the discovery]and I was trying to talk to people on Twitter.”
Bernal and his team published their observations in 2020, naming it the Arsia Mons Extended Cloud, or AMEC for short. With the cloud spanning 1,100 miles, scientists believe it may be the longest cloud in the Solar System. That work was continued with a second report. recently published(Opens in a new window) into Journal of Geophysical Research: Planetsreveals how the volcano created this extraordinary cloud, alone on otherwise cloudless southern Mars at that time of year.
The tweet may have been deleted
(opens in new tab)
(Opens in a new window)
“There were people who thought the ESA was fake.”
How scientists discovered the long cloud of Mars
For decades, the icy cloud came at sunrise on the western slope Arsia Mgr(Opens in a new window), an extinct volcano. The ancient mountain, which once spewed lava, is about 270 miles wide and rises 11 miles into the sky. It dwarfs Mauna Loa, the largest volcano on Earth, at about half its height.
The interesting thing about the giant cloud is how it went unnoticed for so long. But some spacecraft around Mars, like NASA’s Mars Reconnaissance Orbiter, are in sun-synchronized orbits, meaning their cameras can’t take pictures until midday. By then, the transitory cloud that had lasted only three hours in the morning had already disappeared.
The Mars Webcam wasn’t originally designed for science. Its purpose was to provide visual confirmation of this ESA’s Beagle 2 lander(Opens in a new window) In 2003, it was separated from the Mars Express spacecraft. turn on the main camera again(Opens in a new window).

A simple camera, not even intended for science, on the European Space Agency’s Mars Express spacecraft captured a picture of a giant cloud.
Credit: ESA
As the southern Martian spring feels, the cloud grows and stretches, like a steam locomotive over the top of a mountain. Then, within a few hours, the cloud completely disappears in the warm sunlight.
The miracle of nature became a kind of inspiration for the young scientist who received his doctorate. Although the realist in him said recreational space travel was impractical, even unethical given the world’s climate problems, he couldn’t help but draw what the cloud might look like from Earth.
“I imagine what it would be like for a small civilization to have this giant cloud at the same time every year, as if the solstice is like a coat to them,” he said with a smile. “That’s the imagination part.”
The tweet may have been deleted
(opens in new tab)
(Opens in a new window)
Why does Arsia Mons on Mars form a giant cloud?
But what is this strange, stringy cloud doing?
For starters, not smoke caused by a volcanic eruption. Scientists have known for a long time Volcanoes of the Red Planet(Opens in a new window) they die. Rather, it’s what’s called the “orographic effect”: the physics of air rising over a mountain or volcano.
The researchers performed a high-resolution computer simulation of the impact of Arsia Mons on the atmosphere. Strong winds whip at his feet, creating gravity waves. The moist air is then temporarily compressed and blown up the mountainside. These drafts blast out at 45 miles per hour and force temperatures to drop below 54 degrees Fahrenheit. This allows water to condense and freeze about 28 miles above the volcano’s summit.
I want very much Science and technology news delivered straight to your inbox? register for Mashable’s Top Stories newsletter today.
The tweet may have been deleted
(opens in new tab)
(Opens in a new window)
“I imagine what it would be like for a small civilization to have this giant cloud at the same time every year, as if the solstice was like a coat to them.”

The giant Arsia Mons cloud returns every year for about 80 days during the Martian spring.
Credit: ESA
For about five to ten percent of the Martian year, the atmosphere is just right(Opens in a new window) making clouds that help moisture stick to the air with a dusty sky. According to the team’s model, it would be too early in the year and too dry. It would be too late in the year and the climate would be too warm for water to condense.
But while the scientists’ simulation succeeded in creating the cloud under the unique conditions of Arsia Mons, it failed to reproduce the cloud’s long tail. Scientists say that’s the biggest question right now — a mystery that can be solved with spectrometers, devices on spacecraft that determine the types of particles in matter. A closer look at the cloud’s water ice may give researchers more clues.
“I would like to see this cloud with my own eyes, but I know where I am,” Bernal said. “Sometimes we look at space as a utopia. I am happy when I look at it [Earth, through] my spaceship.”