The waters of Iran's Lake Urmia turned from green to blood-red as captured by a NASA satellite.

Lake Urmia, which is located near the border of Iran and Turkey, used to have a distinctive green color. But on July 18, satellite images of the lake showed that it now looks like a large pool of blood.

The deep-red color of Lake Urmia's waters was captured by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the Aqua satellite. According to scientists, the color was due to microorganisms thriving on salt and light.

The waters of Lake Urmia have receded during the past several years. The lake has lost nearly 70 percent of its surface area, and the shrinking has caused the waters to become saltier, especially during the summer, NASA's Earth Observatory said.

NASA scientists are suspecting that the bacteria family called Halobacteriaceae and the algae family Dunaliella are responsible for Lake Urmia's deep red color.

According to Mohammad Tourian, a scientist at the University of Stuttgart in Germany, the algae Dunaliella salina had caused the same red stain in Lake Urmia in the past years.

"In conditions of high salinity and light intensity, the microalgae turns red due to the production of protective carotenoids in the cells," Tourian said in a statement.

But NASA's Earth Observatory said that Halobacteriaceae, which are often found in waters that are saturated with salt, could also be the culprit, as large amounts of the bacteria can turn large bodies of water red.

According to scientists, the waters of Lake Urmia has turned from green to red and back several times in the past. But a red Lake Urmia is likely to be common now, as drought and water diversion for agriculture have reduced the amount of fresh water flowing into the lake.

Lake Urmia is not the only body of water to have red stains caused by microbes.

In 2013, Utah's Great Salt Lake has turned pink after salt-dwelling microorganisms inhabited the lake.