Findings suggest Mars was once home to life and (maybe) still is

We may be closer than we expect to uncovering the possibility of life on Mars after a new study released by NASA suggests that the Red Planet once hosted live organisms -- and might still.

The study reveals that the planet's early atmosphere had much lower carbon dioxide levels than needed to keep it warm enough for liquid water to last. But this finding is in contrast to an older theory that high atmospheric levels of carbon dioxide were responsible for heating up the planet to allow water to flow.

Evidence of lake-like features identified in the Gale Crater from NASA's Curiosity rover suggest that Mars' surface was once home to river deposits and lake beds - which planetary scientists trace to the presence of water billions of years ago.

But scientists also wonder how a "young sun" -- shining weaker than today -- could heat the planet's atmosphere enough to allow water to remain in liquid form.

See newly released photos of Mars from NASA

"This leads to the question of how the surface of ancient Mars, faintly heated by a young sun, was kept warm enough to allow an active hydrological cycle, without substantial amounts of a key greenhouse gas in the atmosphere," the authors stated in the study.

So far, scientists have outlined two possibilities to explain the recent discovery: either their climate models are missing a key element that prompted Mar's surface to heat, or, the evidence gathered from hypothesized lake-like features in the Gale Crater were not actually caused by liquid water.

Still, results from the the rover's exploration within in slopes of the planet -- including mudstone, siltstone and sandstone -- suggest a lake bed was present less than 4 billion years ago during Mars' believed wet period.

SEE ALSO: Astronomers believe strange new signals coming from space are probably aliens

"The watery environments that once occupied the floor of Gale Crater look like they were pretty hospitable to life — not too hot, not too cold, not too acid, not too alkaline, and the water probably was not too salty," said study lead author Thomas Bristow, a planetary scientist at NASA's Ames Research Center in Moffett Field, California.

But with life virtually everywhere on Earth that water is present, scientists still concur that these findings raise the possibility of life on Mars.