Scientists have once again spotted a thin, long cloud over the Arsia Mons volcano on Mars. The scientists have determined the mysterious cloud consists of water ice, but they don’t know why it only forms in the early morning, nor how long it’s been a feature of the Red Planet.
Gizmodo reported on the sighting, which was made by the European Space Agency’s Mars Express orbiter. Mars Express, pictured in the digital rendering below, has been in orbit around Mars since 2003. The orbiter’s made numerous other observations, including one pointing to still-active groundwater beneath the planet’s surface.
“We have been investigating this intriguing phenomenon and were expecting to see such a cloud form around now,” Jorge Hernandez-Bernal, PhD candidate at the University of the Basque Country in Spain, said in an ESA announcement. Hernandez-Bernal is in charge of an ongoing study using Mars Expresses’ Visual Monitoring Camera (VMC).
A mysteriously long, thin cloud has again appeared over the 20-km high Arsia Mons volcano on Mars, revealed in images captured by the @esamarswebcam on #MarsExpress— ESA Operations (@esaoperations) July 29, 2020
Despite appearances, the ESA says the cloud does not coincide with any activity from the nearly 12-mile-high Arsia Mons. Rather, the cloud forms as wind moves past the inactive volcano’s leeward slope. (For those wondering, while the Martian atmosphere is thin, it still contains trace amounts of water vapor.)
The elongated cloud—dubbed Arsia Mons Elongated Cloud or AMEC—forms above Arsia Mons every Martian year around Mars’ southern summer solstice. Like Earth’s Southern Hemisphere’s summer solstice, Mars’ occurs when the Sun is in its most southern position in the Martian skies.
Repeating for 80 Martian days (or Sols), the elongated cloud forms every morning and follows a rapid daily cycle. After collecting for approximately three hours, the cloud dissipates completely only a few hours later.
Looking ahead, Hernandez-Bernal and his colleagues are going to continue studying the mysterious cloud. They’re hoping to understand why the cloud forms in the early morning, as well as how long it’s existed on Mars. And for those who want more photos of AMEC, the ESA has plenty on its Flickr page.
What do you think about this elongated cloud above Arsia Mons volcano on Mars? Do you have any ideas as to why it forms in early mornings? Let us know your thoughts in the comments!
Feature image: European Space Agency