Astronomers have found more evidence that Mars was wet and warm in the ancient past, but the discovery comes with a twist: The water may have flowed below the Martian surface, rather than on top of it.
The new study, which analyzed clay deposits on the Red Planet, revealed that the surface of Mars may have been dry and arid even in its distant past, with lakes and rivers dotting the Martian landscape for only brief periods.
Water-carved landforms on Mars are just one source of evidence that liquid once existed on the planet. Orbiting satellites have also found beds of clay, created by chemical interactions between volcanic rock and water.
To read more, click here.