Researchers at the American space agency made the discovery after the Mars Exploration Rover Spirit became stuck in wet ground on the red planet earlier this year.
Astronomers have become excited by the latest discovery, which they say proves that water favourable for life formed on the red planet more recently than previously thought.
Nasa’s latest study, reported in the Journal of Geophysical Research, concluded the liquid likely formed from melting snow, which then trickled into the subsurface and dissolved.
It contained several minerals including hematite, silica and gypsum while ferric sulphates, which are more soluble, also were carried down by the water.
None of these minerals are exposed at the surface, which is covered by windblown sand and dust.
“On Earth … hydrothermal systems provide the environmental conditions, water, nutrients and energy sources needed to sustain robust microbial communities,” concluded the Nasa team, who are based at Nasa’s Jet Propulsion Laboratory, Pasadena, California.
“It seems likely the region (on Mars) … may have likewise supported a habitable environment.”
According to Nasa, the Mars explorer became stuck in April last year when its left wheels broke through the surface’s crust called “Troy” and fell into soft sand below.
The soil exposed by Spirit’s spinning wheels carries clues that Mars may still be wet.
The seepage could have happened during cyclical climate changes in periods when Mars tilted farther on its axis.
"Liquid water and life kind of go together," said Ray Arvidson, of Washington University in St. Louis, who was involved in the project.
Nasa abandoned plans to extract the rover earlier this year.