To detect the lakes, a radar instrument on Mars Express sent out radio waves to the red planet's surface, which were then reflected back in a certain way depending on the material present there.
The high reflectivity detected by the team of researchers suggests there are large bodies of liquid water trapped beneath the surface.
"The possibility of extended hypersaline water bodies on Mars is particularly exciting because of the potential for the existence of microbial life," the team said.
Researchers believe the water there is salty, allowing it to stay liquid even in Mars' frigid temperatures.
Scientists believe the findings indicate the possibility of a much larger network of ancient underground lakes — which could be millions or even billions of years old, when Mars was warmer and wetter, like Earth. .
Water cannot currently remain stable on Mars' surface due to its lack of a substantial atmosphere, but the presence of liquid water on Mars means there is potential for life.
"And if there was water, there was the possibility of life."
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