When snow shut down one of Earth’s most advanced telescopes high in Chile’s Atacama Desert, the surprise was not just that the instruments went dark, but that it happened in a place famous for almost never seeing clouds at all. The storm turned a landscape built for clear, bone-dry skies into a whiteout, forcing astronomers to abandon precision observations and focus instead on basic survival and safety. For a facility designed to stare deep into the universe, the sudden need to simply ride out the weather felt as jarring as the snow itself.
The shutdown underscored how even the most carefully chosen scientific sites are not immune to a climate system that is becoming harder to predict. What unfolded on the Chajnantor plateau was a rare collision between extreme Earth weather and the delicate machinery we rely on to study distant galaxies, and it caught the observatory’s planners, and much of the astronomy community, off guard.
Why the driest desert became a snow globe
The Atacama Desert is known as one of the driest places on Earth, a plateau where some weather stations have gone years without measurable rain and where astronomers count on cloudless nights as a kind of natural infrastructure. That is why the sight of dunes and salt flats buried under a white layer of powder felt so surreal, turning the usual rust and ocher palette into something that looked more like the Andes in midwinter than the Atacama Desert that observatories were built to exploit. Satellite images captured how a rare storm spread a bright, reflective blanket across the region, confirming that this was not a local flurry but a broad weather event that transformed one of the planet’s most arid landscapes into a temporary snowfield, as documented in rare snowfall imagery.
Climatologists point to the way winter storms can occasionally tap moisture from the Pacific and push it inland, lifting it over the Andes until it cools and falls as snow even over deserts that almost never see precipitation. In this case, the system delivered enough cold air and humidity to overcome the Atacama’s usual dryness, dropping accumulations measured in tens of centimeters rather than a light dusting. Reports from the high plateau described snow depths of roughly 20 to 80 centimeters in some spots, a range that matches the kind of heavy, wet fall that can overwhelm infrastructure in places unaccustomed to plowing or de-icing, a pattern that local meteorologists linked to winter storms fueled by the Pacific.
ALMA’s sudden slide into survival mode
High on the Chajnantor plateau, the Atacama Large Millimeter/submillimeter Array, better known as ALMA, is built to capture faint energy from the cold universe, not to withstand a full-on snowstorm. The facility consists of 66 precisely engineered antenna dishes spread across the plateau, each one relying on clear, dry air to pick up millimeter and submillimeter wavelengths from distant galaxies, star-forming clouds, and black holes. When the snow began to fall in earnest, those dishes were suddenly exposed to loads and wind patterns they were never meant to endure, turning a world-class observatory into a field of vulnerable metal structures at risk of damage from ice buildup and gusts.
Operators responded by halting scientific observations and shifting the array into what they describe as survival mode, a protocol that reorients the antennas downwind and locks them into safe positions to minimize stress on their moving parts. Scientific operations had already been suspended since Thursday, June 26, as the storm intensified, and the shutdown extended for several days while crews waited for conditions to improve and access roads to clear. The decision to prioritize safety over data meant that one of the world’s most powerful radio facilities, often described as the world’s most powerful radio telescope, went dark at the height of the storm, a step confirmed when officials said scientific work had been paused and the site placed into a protective configuration.
Inside the world’s most powerful radio telescope
To understand why the shutdown mattered, it helps to look closely at what ALMA actually does on a clear night. The array’s 66 dishes work together as a single instrument, using interferometry to combine signals and achieve the resolution of a much larger telescope, which allows astronomers to map protoplanetary disks, measure the chemistry of distant galaxies, and probe the cold gas that fuels star formation. The site’s altitude on the Chajnantor plateau, in the Atacama Desert, was chosen precisely because the air is so thin and dry that it absorbs very little of the millimeter and submillimeter radiation ALMA is tuned to detect, giving it a clear view of the cosmos that few other locations can match.
When snow and ice coat those antennas, the delicate balance that makes such observations possible is disrupted, both physically and electronically. Moisture in the air increases background noise, while snow on the dishes can scatter or block incoming signals, turning what should be crisp images into unusable data. That is why the rare storm that swept across the plateau did not just inconvenience astronomers, it effectively blinded one of Earth’s most advanced telescopes and halted observations of targets that had been scheduled months in advance. Accounts of the event describe how one of the world’s most advanced telescopes simply went dark, with observations halted for several days while teams assessed the impact.
How the storm blindsided planners
ALMA’s designers knew they were building in a harsh environment, but the harshness they planned for was thin air, intense ultraviolet radiation, and bitter cold, not deep snow. The Atacama Desert is so dry that much of its moisture normally vanishes through sublimation, the process by which ice turns directly into vapor without melting, and that history of aridity shaped expectations about what kind of weather the site would face. When the storm arrived with enough strength to drop significant accumulations on the Chajnantor plateau, it exceeded what many on-site staff had experienced in their careers, turning the usual risk calculations on their head and forcing them to improvise responses in real time, a dynamic described in detail in coverage of snow in the Atacama Desert.
Forecast models had flagged the possibility of winter storms, but the intensity and persistence of this particular system appear to have surprised both meteorologists and observatory managers, who were more accustomed to planning around dust storms and high winds than around heavy, wet snow. The fact that scientific operations had to be suspended for days, and that access to the high-altitude camp became extremely difficult, shows how quickly a site optimized for clear skies can become isolated when the weather shifts outside its usual bounds. Reports from the region describe how extreme conditions paralyze ALMA, underscoring that even the best prepared facilities can be caught off guard when rare events push beyond historical norms.
What shutdown looked like on the ground
On the plateau itself, the shutdown was as much a logistical challenge as a scientific one. Staff had to secure the antennas, protect sensitive electronics from moisture, and ensure that power and communications remained stable while the storm raged. At the same time, they had to think about basic human needs at high altitude, where oxygen is scarce and any evacuation or resupply is complicated even in good weather. With access roads buried and visibility reduced, simply moving people and equipment between the high site and lower support facilities became a slow, risky process, and managers had to weigh the urgency of repairs against the safety of crews who would have to work in freezing, low-oxygen conditions.
The observatory’s survival protocols, which include reorienting dishes downwind and locking them into safe positions, were designed to handle strong gusts and occasional frost, but the volume of snow forced teams to adapt those procedures on the fly. They had to monitor snow buildup on structural elements, check for ice on moving joints, and watch for any signs that the weight of the accumulation might stress components beyond their design limits. Accounts of the event describe how as part of this protocol, operators carefully tracked snow buildup and wind, underscoring that the shutdown was not a simple on-off switch but a complex, ongoing effort to keep a fragile system intact until the skies cleared.
Other telescopes felt the same storm
ALMA was not the only observatory to feel the impact of the rare winter storm. Across the Atacama region, other high-altitude facilities found themselves suddenly surrounded by snow, including the Southern Astrophysical Research, or SOAR, Telescope in Chile, which sits on a neighboring peak. Images from that site show the dome and surrounding infrastructure coated in white, a striking contrast to the usual bare rock and scrub that frame the instrument. For astronomers used to thinking of the Atacama as a near-perfect observing platform, the sight of multiple observatories simultaneously blanketed by snow was a visual reminder that even the driest deserts can experience weather extremes, a point highlighted in coverage that asked why such scenes are so striking.
Farther across the desert, lower elevation areas that almost never see precipitation also reported a rare dusting, with photographs showing cacti and desert shrubs poking through a thin layer of snow. Those images circulated widely because they seemed to invert the usual narrative of the Atacama as a place of unrelenting dryness, where even hardy plants struggle to survive. Reports described how the Atacama briefly traded its parched look for something closer to a high-latitude steppe, reinforcing the sense that the storm was not just a local anomaly but a region-wide event that touched multiple scientific sites and communities.
NASA’s orbital view of a once-in-a-decade event
While ground crews wrestled with snowdrifts and frozen equipment, satellites in orbit provided a broader perspective on what was happening below. Instruments that normally track vegetation, soil moisture, and atmospheric conditions captured the sudden brightening of the Atacama’s surface as snow increased its reflectivity, offering a clear before-and-after snapshot of the storm’s footprint. Those images helped confirm that the snowfall was both extensive and unusually intense for the region, supporting the sense among local observers that they were witnessing something that might only occur once in a decade or longer, a rarity underscored by NASA captures rare snowfall analyses.
From my perspective, that orbital vantage point is crucial because it ties a dramatic local story to the larger climate system. Seeing the Atacama Desert, long held up as a benchmark for aridity, suddenly appear as a bright, snow-covered patch on global maps forces scientists to ask whether such events are becoming more likely as patterns of moisture transport and temperature shift. The fact that the same storm that shut down ALMA also showed up clearly in satellite data means researchers can study its dynamics in detail, comparing it to past events and testing whether the atmospheric ingredients that produced it are becoming more common. That kind of analysis is already underway in studies of one of the driest places on Earth, where even a single snowstorm can offer valuable clues about how a changing climate might reshape extremes.
What the shutdown means for science and climate risk
In the short term, the snowstorm’s most obvious impact was the loss of observing time at a facility that is heavily oversubscribed, with astronomers around the world competing for every available hour on ALMA’s schedule. Projects that had been carefully timed to catch transient events, such as flares from young stars or changes in the chemistry of distant gas clouds, had to be postponed or abandoned, and some of that lost opportunity cannot be recovered. For a telescope that often operates as part of global campaigns, coordinating with instruments like the Very Large Telescope or space-based observatories, an unexpected shutdown can ripple through multiple research programs, forcing teams to rework plans and, in some cases, accept that a particular alignment or event will not be observed again.
Over the longer term, I see the episode as a warning about how climate variability and change can affect even the most carefully chosen scientific sites. If storms like this become more frequent or more intense, observatories in the Atacama Desert may need to invest in new infrastructure, from improved snow clearance and drainage to reinforced antenna structures and more robust survival protocols. The fact that one of the world’s top radio observatories had to put its work on hold since June 26 because of snow should prompt a broader conversation about resilience, not just in Chile but at other high-altitude sites that have historically relied on stable, predictable conditions.
A desert that keeps rewriting its own script
The Atacama has always been a place of extremes, but those extremes are now taking on new forms that challenge long-held assumptions. In the past, the desert’s defining feature was its lack of water, a dryness so profound that some valleys resemble Mars more than any other place on Earth, and that history shaped everything from how instruments were designed to how they were maintained. The recent snowstorm, however, showed that even in such a setting, water can arrive suddenly and in large quantities, turning a landscape optimized for desiccation into one that must cope, however briefly, with ice and meltwater. Reports of a rare blanket of snow falling in Chile’s Atacama, the world’s driest desert, capture that sense of the desert rewriting its own script.
For me, the image of ALMA’s antennas standing silent under a white sky is a powerful symbol of how intertwined our exploration of the universe has become with the behavior of our own planet. The same atmosphere that can be so transparent to millimeter waves on a clear night can, under the right conditions, turn opaque with snow and ice, reminding us that our view of the cosmos is always filtered through Earth’s changing climate. As scientists sift through data from this event, both from the ground and from orbit, they will not just be asking how to prevent the next shutdown, but also what this rare storm says about the future of extreme weather in places we once thought were almost immune to it, a question that will continue to shape research in the one of the driest places on Earth and beyond.
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