Scientists have been observing a weird cloud on Mars that is so big, it can be seen using telescopes on Earth.

Volcanic Eruption On Mars?

The mysterious cloud, which has appeared over a month ago, is located over the Arsia Mons, a volcano near the equator of the red planet. It stretches about 930 miles.

However, despite its location, scientists believe that the cloud is not coming from the volcano. Arsia Mons is believed to be extinct; its last eruption happened about 50 million years ago or right around the time the dinosaurs had gone extinct on Earth.

Water Ice Cloud Of Mars

Instead, the European Space Agency revealed that the white stripe over Arsia Mons is a water ice cloud and it is a regular occurrence in the area. According to scientists, the cloud is created by the leeward slope of air flow around the volcano. The last time a similar water ice cloud was observed by the Mars Express was in 2015.

The cloud also appeared a few days before the winter solstice in the northern hemisphere of Mars when most of the cloud activity in Arsia Mons and other big volcanoes dissipate. Its appearance also changes throughout the day: longer in the morning and almost parallel to the equator.

The European Space Agency also suggested that the dust storm that engulfed the red planet in a red haze in June and July might have also affected the appearance of the ice water cloud. The cloud is also "sensitive" to the amount of dust in the atmosphere.

Scientists hope to use photos taken by the Hubble Space Telescope from the dust storm in July to study how the dust affected the formation of the cloud and how it will further influence events on the red planet.

A photo of the cloud was taken by the Mars Express's Visual Monitoring Camera on Oct. 10. The High Resolution Stereo Camera, OMEGA, and visible and near-infrared mapping spectrometer onboard the spacecraft also observed the phenomenon from orbit in the past month.

The Mars Express will continue taking photos of the water ice cloud on Mars.