Why an Enormous Martian Cloud Returns Every Spring: Scientists Uncover the Answer

An enormous Martian cloud returns every spring. Scientists now know why.

Scientists have discovered a mysterious cloud that stretches longer than the state of California across Mars’ ruddy cheek. The low-resolution camera on the European Space Agency’s Mars Express probe first captured the enormous cloud in 2018, and it’s been there through the aughts, and even during NASA’s Viking 2 mission in the 1970s. Dubbed the Arsia Mons Elongated Cloud, or AMEC, it spans 1,100 miles and could be the longest of its kind in the solar system. Researchers believe the cloud is created by the orographic effect, where strong winds whip at the foot of an extinct volcano, causing gravity waves and forcing moist air up the mountain. This allows water to condense and freeze at about 28 miles above the volcano’s peak. The cloud appears for about 80 days in Mars’ springtime and then fades away in the warm sunlight. While the realist in astrophysicist Jorge Hernández Bernal says recreational space travel is impractical, he still imagines what it would be like for a little civilization to have this huge cloud every year. Scientists are now trying to use spectrometers to study the cloud’s water ice, in hopes of discovering more about its tail. Bernal says he’s happy looking at the cloud from Earth through his spacecraft.