With the growing variety of samples collected and measurements made by NASA's Mars rovers, the scientific evidence that water once flowed freely on the surface of the Red Planet has mounted.

Still, researchers have had trouble rectifying these liquid water signifiers with the fact that Mars is freezing cold. Even more confusing -- the newest climate models suggest Mars was always icy cold. So, the question remained: when and how was ancient Mars ever warm enough to host liquid water?

New research suggests Martian volcanoes may have helped warm the planet for brief periods of time (for a few dozen or few hundred years at a time), just long enough to allow water to exist in a liquid state.

Unlike on Earth, where major volcanic activity has a cooling effect, an influx of volcanic gases allowed Mars' atmosphere to better trap heat, not reflect it.

"We looked at Mars' early atmosphere being dusty, and our calculations suggest a lot of the [volcanic plume] minerals like sulfur dioxide and sulfuric acid will adhere to these dust particles, reducing their ability to reflect the Sun's rays, delaying cooling," study author James Head, a geologist at Brown University, told ABC Science.

"We calculate that 30 percent of Mars was resurfaced by lava flows, that's a lot of lava, and it can erupt over relatively short periods of time," Head added. "It comes out as flood basalts and can have a huge affect on a planet's atmosphere."

Even without volcanoes, summer afternoons were likely warm enough on early Mars to allow for short stints of liquid water.

"The average yearly temperature in the Antarctic Dry Valleys is way below freezing, but peak summer daytime temperatures can exceed the melting point of water, forming transient streams, which then refreeze," Head said in a press release. "In a similar manner, we find that volcanism can bring the temperature on early Mars above the melting point for decades to centuries, causing episodic periods of stream and lake formation."

The research of Head and his colleagues was published this week in the journal Nature Geoscience.