German researchers have found salt -- a signature chemical for seawater -- in ice grains from vapor jets streaming out of surface cracks, providing the strongest evidence yet of a liquid water reservoir beneath the moon's frozen crust.

"Our picture of its sub-surface must now be expanded to include the possibility of misty ice caverns floored with pools and channels of salty water, lurking beneath the tiger stripes," he wrote in a commentary on the two scientific papers.

"What else may lurk in those salty pools, if they exist, remains to be seen."