A new analysis finds that a planned green hydrogen and ammonia complex in northern Chile would have added light, vibration, and dust to one of the darkest telescope sites on Earth.
Those changes would have made it harder for powerful observatories there to detect faint objects and capture sharp images, reducing what astronomers could discover.
Paranal under pressure
On a desert ridge in northern Chile, Paranal’s observing platform sits within about 16 miles (26 kilometers) of the planned INNA industrial energy complex, a large project designed to produce green hydrogen and green ammonia.
From that close range, the European Southern Observatory (ESO) calculated how lighting, wind turbines, and dust would reach nearby telescopes.
In March 2025, ESO concluded that developers could not adequately mitigate those combined impacts at the proposed location.
Once extra light, vibration, or dust enters the system, telescopes cannot filter it out later, so prevention matters.
How dark sky works
In its ranking of 28 major observatories, the report said only six sat under 1% artificial brightening. Natural glow from the Moon and upper air sets a baseline, while light pollution raises it.
At 1% contamination, one out of every 100 sky photons comes from cities, and a telescope cannot tell them apart.
Much of that ranking focused on the V-band, a standard green filter in astronomy, because artificial brightness shows up clearly there.
The cumulative light effect
By 2024, ESO’s models showed artificial sky brightness had already climbed three to almost four times since 2012.
Even light sources 31 to 62 miles (50 to 100 kilometers) away added scattered photons above the desert.
With ideal fixtures, INNA would have raised artificial brightness another 5% to 55%, and up to 269% if lights brightened fivefold.
During thin cirrus clouds that cover about 13% of observing time, the report predicted INNA lighting could look 1.5 to 2.8 times brighter.
Wind turbines and precision
A total of 70 wind turbines led ESO to flag ground vibration as a risk to precision observations at Paranal and the nearby Armazones peak.
Vibration matters most for an interferometer, a system that merges light from separate telescopes, because timing errors smear fine detail.
In the report’s wind-farm scenario, wind turbines likely exceeded vibration limits for the Very Large Telescope Interferometer and the 128-foot (39-meter) Extremely Large Telescope.
Because the system combines optical beams in real time, astronomers cannot use later processing to correct shaky foundations, leaving fewer nights suitable for the highest resolution.
Wakes roughen the air
Wind farms do not stop at the fence line, and their wakes have been detected 34 to 62 miles (55 to 100 kilometers) downwind.
That moving air can worsen seeing the blur astronomers measure in starlight, by making star images spread out on detectors.
Under good conditions, estimated turbulence rose 17% for 0.5 arcseconds and 43% for 0.3, pushing typical episodes toward 0.4 to 0.6.
Heat above INNA solar panels could add more turbulence, because air about five degrees Fahrenheit (three degrees Celsius) warmer tends to rise and mix.
Dust hits the optics
During INNA construction, ESO projected airborne particle levels would rise about 75% for coarser dust and 73% for finer dust.
Dust harms telescopes when grains stick to mirrors, lowering reflectivity, the fraction of light a surface bounces back.
At Paranal, the report linked that burden to about a 2.5% loss of light throughput and 2% more cleaning downtime.
The Cherenkov Telescope Array Observatory South site faced the sharpest hit because its mirrors lack full enclosures against dust.
Proximity defines impact
Even small design changes could not erase the core problem, because INNA sat too close to the observatory ridges.
Distance matters because light scatters through air and vibration travels through rock, so both weaken only when sources sit farther away.
ESO also wrote that small lighting adjustments near Armazones could bring contamination back near 1% for the Extremely Large Telescope.
Without relocation, the report concluded remaining impacts would still be substantial, which turns site selection into a policy issue.
A project gets dropped
In February 2026, an ESO announcement said AES Andes would step back from INNA and focus on its renewable portfolio.
Chile’s environmental assessment service still had to close out the paperwork, but ESO expected withdrawal soon would make the cancellation official.
“When the cancellation is confirmed, we’ll be relieved that the INNA industrial complex will not be built near Paranal,” said Xavier Barcons, Director General of ESO.
Ending the project gave the telescopes their best chance to keep current conditions, even as regional development continues adding light.
Rules for shared deserts
INNA also exposed how fast a special site can lose value when planners treat darkness and quiet as free resources.
Protecting observatories means controlling outdoor lighting, limiting dust, and placing large turbines far enough away that wakes fade.
Barcons said green-energy projects could coexist with observatories when planners kept enough distance between industrial sites and telescopes.
Clear protection rules would keep future energy projects from repeating the same conflict, especially as Chile expands renewable capacity.
Keeping skies clear
The INNA analysis put hard numbers on risks that sound abstract, then tied each one to lost observing power.
Future reviews can use those same thresholds to draw buffer distances early, before equipment is built and hard choices follow.
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