Astronauts capture glowing salty pink Valentine’s Day ‘hearts’ in Argentina — Earth as seen from space

This photo of the amorous astronaut was first published by NASA on Valentine’s Day 2025, highlighting a pink heart-shaped salt lake in Argentina.

Salinas Las Barrancas, also known as Laguna de Salinas Chicas, is a shallow salt lake in the lowland plains of Argentina’s Buenos Aires province, approximately 53 km (33 miles) west of the port city of Bahia Blanca.

The lake bed is approximately 10 km in diameter at its widest point and regularly fills with water after heavy rains. But NASA’s Earth Observatory says the region’s strong sunlight quickly evaporates this liquid, exposing salt flats rich in crystals mined by locals.

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In this photo, the lake appears almost empty due to its bright pink color, but a 2022 Smithsonian Magazine article about similarly colored salt lakes says this is likely the result of an imbalance between Dunaliella salina, a type of dark red algae that grows in most salt lakes on Earth, and other microorganisms in the water.

“We have a rainy season and the salinity levels drop. [because there’s more water in the ponds]. When the salinity is low, Dunaliella survives and the ponds appear reddish-brown,” Lilium Casillas Martínez, a microbiologist at the University of Puerto Rico Humacao, told Smithsonian, explaining the color of similar salt ponds in Puerto Rico. “During the dry season, it gets really salty. The Dunaliella dies and the archaea and bacteria take over. Then it goes pink, pink, pink.”

Local residents mine up to 330,000 tons (300,000 metric tons) of salt from the flatlands of Salinas Las Barrancas twice a year, during the region’s rainy season, according to a 2019 feature on the lake by Argentine news site La Nación. Most of this salt will be replenished by the next heavy rain, and experts predict that mining there will last for at least 5,000 years.

Mining is primarily done using traditional processes, such as scraping salt from the surface of the plain using hand tools. Workers must take precautions to protect their eyes and skin from the strong sunlight reflecting off the pure white crystals. “Salt becomes part of your life,” Chepo, a local worker, told La Nacion (translated from Spanish). “For others it’s a hellish place, but for me the salt flats are home. You get used to being blind.”

Due to the high salinity of Salinas Las Barrancas, very few people can survive there. However, the Earth Observatory says some salt-tolerant plants grow around the edges of the lake.

It’s also home to brightly colored birds, including the bright yellow cardinal (Gubernatrix cristata) and the bright pink Chilean flamingo (Phoenicopterus chilensis). These birds feed on small crustaceans that are rich in carotenoids (organic pigments synthesized by plants, algae, and bacteria).

These particular carotenoids are derived from the Dunaliella algae that small crustaceans feed on and naturally produce both red and yellow pigments. If these pigments were not included in the diet from birth, both bird species would have different colors. Yellow cardinals are born red, and flamingos are born grayish-white.