NASA issued a study today that said if life ever existed on Mars, the longest lasting environments were most likely below the planet's surface.
The hypothesis comes from analyzing tons of mineral data gathered over the years from more than 350 sites on Mars gathered by NASA and European Space Agency Mars space probes.
More on space: 8 surprising hunks of space gear that returned to Earth
The idea is that "Martian environments with abundant liquid water on the surface existed only during short episodes. These episodes occurred toward the end of a period of hundreds of millions of years during which warm water interacted with subsurface rocks. The types of clay minerals that formed in the shallow subsurface are all over Mars but the types that formed on the surface are found at very limited locations and are quite rare. This has implications about whether life existed on Mars and how the Martian atmosphere has changed."
NASA says another clue is the detection of a mineral called prehnite which forms at temperatures above about 400 degrees Fahrenheit (about 200 degrees Celsius). These temperatures are typical of underground hydrothermal environments rather than surface waters., NASA said.

"If surface habitats were short-term, that doesn't mean we should be glum about prospects for life on Mars, but it says something about what type of environment we might want to look in," said the report's lead author, Bethany Ehlmann, assistant professor at the California Institute of Technology and scientist at NASA's Jet Propulsion Laboratory. "The most stable Mars habitats over long durations appear to have been in the subsurface. On Earth, underground geothermal environments have active ecosystems."
Follow Michael Cooney on Twitter: nwwlayer8 and on Facebook
Layer 8 Extra
Check out these other hot stories:
NASA looking at building tractor beams for space
Harvard to welcome back Facebook CEO Mark Zuckerberg
US intelligence group seeking cutting-edge, secure chip development
Harvard, MIT to get shots at IBM Watson
The ultimate in man v. machine moments
DARPA offers $50,000 prize if you can figure out these shredded puzzles
Can humans alter climate change?
NASA: "Interplanetary bogeyman" comet Elenin is no more; it's an ex-comet
US to fund aggressive technology that cuts solar power costs 75%
Air Force wants to understand impact of automated systems the human psyche
After the iPhone, ex-Apple engineers built world's ultimate thermostat
IBM turns up Watson-like natural language healthcare analytics
New copper theft foil: Bust the drivers
Gartner: 16 long-held IT business practices you need to kill
Gartner: The top 10 strategic technology trends for 2012