Unexpected Snow Shuts Down World's Largest Telescope in Driest Desert

• The Atacama Desert, one of Earth's driest regions, experienced unexpected snowfall in July 2025, astonishing scientists and locals.
• The rare event, caused by a cold-core cyclone, forced the Atacama Large Millimeter/submillimeter Array (ALMA) to pause operations and enter "survival mode."
• Satellite images from NASA’s Landsat 9 and ground observations documented the snow on the Chajnantor Plateau, home to ALMA.
• Scientists were surprised by how even light, short-lived snow disrupted advanced scientific equipment in such an extreme ecosystem.
• This "once-in-a-lifetime" observation highlights climate variability and prompts further studies on climate change links and future observatory planning.

Why It Matters: Rare snow in Atacama Desert forced ALMA shutdown, highlighting extreme climate variability.