糖心视频

The largest salt flat in the world is Salar de Uyuni in Bolivia, a popular tourist attraction due to its stunning mirror-like surface when covered with a thin layer of water. While considered by many to be the "world's largest natural mirror," this claim had not been scientifically verified. Now, in a study in the journal Communications Earth & Environment, scientists set out to confirm the effect and discovered that the surface is more complex than previously thought.

Most of the evidence of the mirror effect is anecdotal, coming from tourist photos of people standing on the flats with the water perfectly reflecting the clouds, sky, mountains and themselves. It's difficult to study the phenomenon because the vast interior of the salt flat is often inaccessible during the wet season. So the researchers developed a two-part approach to overcome this challenge.

First, they used data from Sentinel-3 satellites, which are equipped with radar altimeters that send out radar pulses and measure the amount of the signal that bounces back. The stronger the return signal, the smoother the surface. They analyzed more than 390,000 radar measurements from 2016 to 2024.

To ensure the accuracy of their satellite data, the research team conducted field tests during peak wet season in February 2024. This trip was timed to coincide with a Sentinel-3 satellite passing directly overhead. On the ground, scientists used an optical tool to measure the water's surface. A drone also captured images of the sun's reflection to provide visual confirmation of its smoothness. The on-the-ground measurements demonstrated that when the satellite detected a strong radar signal, the surface was indeed a mirror.

So what exactly did they find?

"The Salar de Uyuni is not a vast uniform mirror for the radar altimeter," wrote the researchers in their paper. "Therefore, it is also likely that it is not a large mirror for optical wavelengths, as suggested in the literature."

Instead of being a uniform mirror, the salt lake's surface changes from place to place and over time. The smoothest, most mirror-like conditions occur after significant rainfall and before the water has had a chance to evaporate. The researchers found a strong correlation between periods of high rain and the mirror effect, confirming that it is a direct result of the region's climate patterns. They also concluded that the best time to see the mirror is from late January to early March.

One of the more surprising findings was that the wind didn't spoil the mirror effect. You would expect a breeze to cause ripples on the surface to break up the mirror, but this doesn't happen. The researchers suggest this is because the water is so shallow that it prevents waves from forming, even in a breeze.

漏 2025 Science X Network