Is this distant desert really the largest mirror in the world?

Even if you do not know the Salar of Uyuni by his name, there is a good chance that you have seen a photo. Tourists flock to this solid salt flat in Bolivia to take images of its mirror -shaped surface, only visible when covered with a thin layer of water.

Salar de Uyuni is the largest salt desert in the world, and for years, people supposed that it was also the largest natural mirror in the world. I mean, check it for yourself-you will see what I mean in the video below.

The wet surface is incredibly reflective. That said, no one had never decided to scientifically prove that it is the largest natural mirror in the world – until recently.

Is Salar de Uyuni really a giant mirror?

In a new study published on September 19 in the journal Nature Communications Earth & Environment, researchers used data from Sentinel-3 satellites from the European Space Agency to seek empirical evidence of the Uyuni Salar mirror, or its specular reflection. They used satellite data because the vast interior of the salt apartment is often inaccessible during the rainy season, which makes it difficult to study this phenomenon.

Each of these satellites with observation of the twin land is equipped with radar altimeters – instruments that radiate radar pulses to earth and measure the time it takes for the rebounded signal. The higher the return signal, the more the surface below.

The researchers, led by Stefano Vigrudelli of the Institute of Biophysics of the National Research Research Council, analyzed more than 390,000 radar measures between 2016 and 2024. In February 2024 – The Picles rainy season – they carried out tests on the ground to validate their satellite observations, using an optical tool to measure the sweetness of the surface of the water. Drone photography also provided a visual confirmation of sweetness by capturing images of the sun’s reflection out of the water.

The verdict? It’s complicated

The researchers’ results show that despite his naked eye appearance, Salar de Uyuni is not a uniform mirror with radar wavelengths. Therefore, it is probably not a uniform mirror for optical wavelengths either. On the contrary, the reflectivity of the surface of the water evolves spatially and temporally.

The mirror formal conditions occur after significant precipitation and before the water had the possibility of evaporating, according to the researchers. The correlation between periods of heavy rain and the mirror effect suggests that it is the direct result of regional climate models, which led the authors to conclude that the best time to see the mirror is from the end of January to early March.

Since this phenomenon only arises in specific conditions and does not affect the whole Salar of Uyuni, it is difficult to say if it is in fact the biggest natural mirror in the world at any time. This does not mean that it is not exceptionally cool, however.

One of the most intriguing results of this study is that the wind does not disturb the mirror effect, probably because the water is so shallow that the ripples cannot form. Researchers hope that future studies will study this and offer more knowledge of the unique characteristics that give birth to this natural wonder.