It is clear, based on geological evidence, that liquid water once flowed on Mars. Some have used this evidence to try and paint a picture of a once green and vibrant planet that has since been beset by some environmental tragedy. Such a picture, however, simply doesn’t make sense given what is known about the Red Planet.

Mars is, and appears to have always been very cold. It is 50,000 miles further from the Sun than the Earth is, with no real atmosphere to hold in the heat. The Sun was also dimmer in the ancient past than it is currently, which means that less heat would have reached Mars.

New research from scientists at Brown University and the Weizmann Institute of Science in Israel attempts to reconcile the picture of a barren, frozen planet with clear evidence that water once flowed there. The research, published in Nature Geoscience, suggests that periods of volcanic activity may have warmed the planet enough to allow brief water flows.

“These new climate models that predict a cold and ice-covered world have been difficult to reconcile with the abundant evidence that water flowed across the surface to form streams and lakes. This new analysis provides a mechanism for episodic periods of heating and melting of snow and ice that could have each lasted decades to centuries,” said James W. Head in a statement. Head is a professor of earth, environmental and planetary sciences at Brown University and, along with Weizmann’s Itay Halevy, a co-author of the new paper.

On Earth, widespread volcanic activity generally leads to cooler temperatures. The thick ash and sulfuric acid reflect the suns rays back into space. On Mars, however, the researchers believe that volcanism could have caused warming temperatures.

Head and Halevy created a model of how sulfuric acid might react with Mars dusty atmosphere. The researchers were able to show that sulfuric acid particles would have glommed onto dust particles, reducing their ability to reflect the sun’s rays. At the same time sulfur dioxide gas would have caused a mild greenhouse effect.

“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. 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,” said Head.

The researchers believe that these warm periods would have occurred about 3.7 billion years ago.

After years of fieldwork in Antarctica Head also has a suggestion of where life may have existed on Mars, if it ever did.

“Life in Antarctica, in the form of algal mats, is very resistant to extremely cold and dry conditions and simply waits for the episodic infusion of water to ‘bloom’ and develop. Thus, the ancient and currently dry and barren river and lake floors on Mars may harbor the remnants of similar primitive life, if it ever occurred on Mars,” said Head.