What is that California-sized cloud on Mars?

For starters, it's not smoke billowing from a volcanic eruption.
 By   and 
Elisha Sauers
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Massive Mars Cloud
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Thinking about space for too long can be scary and overwhelming. Are we alone? Will we ever be able to live on another planet? Will black holes destroy the universe one day? What should you do if you ever encounter an alien? Don’t worry, our curious science producer will do all the excessive thinking for you, and teach you a thing or two in the process. With the help of experts, our producer will deep dive into all the interesting things that happen, have happened, and will happen in space.


A cloud longer than California streaks across Mars' ruddy cheek. It looks as though an impressionist painter loaded his palette knife with white and scraped a line across the canvas as far as the oily paint would travel.

This is not what astrophysicist Jorge Hernández Bernal first saw in 2018 when the Mars Express Visual Monitoring Camera(Opens in a new window) — affectionately known by the European Space Agency as the Mars webcam(Opens in a new window) — posted a new picture. To the average eye, it was grainy and inscrutable, with the resolution of a standard computer camera circa 20 years ago. But Bernal, who was studying Martian meteorology at the University of the Basque Country in Spain, immediately recognized the shadow as something else: a mysterious weather phenomenon happening on the Red Planet.

It wasn't until researchers looked at the cloud with better equipment that Mars revealed the cloud in all its sprawling glory. The team dug deeper into photo archives, and discovered it had frequently been there. It was there through the aughts, and it was even there during NASA's Viking 2 mission(Opens in a new window) in the 1970s.

Topics NASA

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Elisha Sauers

Elisha Sauers writes about space for Mashable, taking deep dives into NASA's moon and Mars missions, chatting up astronauts and history-making discoverers, and jetting above the clouds. Through 17 years of reporting, she's covered a variety of topics, including health, business, and government, with a penchant for public records requests. She previously worked for The Virginian-Pilot in Norfolk, Virginia, and The Capital in Annapolis, Maryland. Her work has earned numerous state awards, including the Virginia Press Association's top honor, Best in Show, and national recognition for narrative storytelling. For each year she has covered space, Sauers has won National Headliner Awards, including first place for her Sex in Space series. Send space tips and story ideas to [email protected] or text 443-684-2489. Follow her on X at @elishasauers.


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