The European Space Agency (Esa) also plans to send a rover to investigate Mars' habitability.
These under-ice environments may also provide fascinating insights into the potential habitability of some moons in the Solar System.
"Habitability zones are a nightmarishly complicated concept, " said astrophysicist Patrick Young at Arizona State University, who studies planets' suitability for life.
These fluids trapped in the subsurface could have periodically breached the surface in deep basins such as McLaughlin Crater, possibly carrying clues to subsurface habitability.
Eventually, researchers hope to develop a more detailed Planetary Habitability Index that factors in the idea that life might exist under exotic conditions unknown on Earth.
"Statements about a planet's habitability always depend on assumptions, " said Lisa Kaltenegger, an expert on the likely atmospheres of "exoplanets" and a member of the discovery group.
BBC: Kepler telescope spies 'most Earth-like' worlds to date
The astronomers, whose research is detailed in the January issue of the journal Astrobiology, say the effects of tidal heating must be considered when determining an exomoon's habitability.
With the habitability issue out of the way, Curiosity has yet to explore the question of organic molecules, which could indicate life but could also come from other sources.
"The main goal is to try to assess this material in a very general way that will give us an appraisal of the habitability of this environment, " he explained.
Most of what we know about "habitability" -- the ability of an environment to host and support life -- has been studied under the very different conditions on Earth.
In its solar system there is another planet, Gliese-581d, that is also of interest in the search for life, according to the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo.
Uniquely qualified on cutting-edge issues of science and technology, Mr Gore chose to write a courageous book on the dangers of catastrophic climate change and other threats to the habitability of our planet.
"There is no agreement by the astrobiology community on how to measure habitability, " said Abel Mendez, director of the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo, who is working on several planetary indexing systems.
"We have so many more worlds that could be a locus for life, but so much less information upon which to understand the habitability of that world, " said astrobiologist Tori Hoehler at NASA's Ames Research Center in Mountain View, Calif.
"The role of liquid water on Mars is of great importance for its habitability and this study using Mars Express describes a very large zone where groundwater was present for a long time, " said Olivier Witasse, a project scientist with ESA's Mars Express.
MSN: New proof that water existed underground on ancient Mars
To compare alien planets, Dr. Mendez at the Planetary Habitability Laboratory and his colleagues are creating an Earth Similarity Index that ranks worlds by their resemblance to our own planet, on a scale from zero to one, based on their mass, radius, density and surface temperature.
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