It is generally accepted that the surface of Mars was covered in liquid water about four billion years ago, until it lost its atmosphere.
However, the sun was much dimmer then, which makes you wonder if it would have even been possible for liquid water to exist on the fourth planet under those conditions. A new study suggests that liquid water may have once flowed on Mars, but only during short warming periods brought about from volcanic activity. The research was performed by Itay Halevy of the Weizmann Institute of Science in Isreal and James Head of Brown University. The paper was published in Nature Geoscience.
“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,” Head said in a press release. “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.”
The features of liquid water on Mars date back about 3.7 billion years, which is right around when volcanic activity is assumed to have occurred as well. When volcanoes erupt on Earth, the ash and sulfur dioxide particles reflect sunlight, which can cool the planet. The atmosphere of Mars was much dustier, so volcanic activity could have acted differently.
Head and Halevy suggest that the sulfur may have stuck to the airborne dust particles, causing them to clump together and allow the sunlight to pass through. The pair developed models using sulfuric acid which show this could have been plausible. Though the sulfur wouldn’t reflect the sunlight, it would have been enough to create a small greenhouse effect and warm the planet near the equator.
The warming effect of these volcanoes likely only lasted a few decades to a few centuries, but could have been enough to allow liquid water to flow. Head likens it to the McMurdo Dry Valleys in Antarctica, where conditions are typically dry and extremely cold, but ephemeral minor heat waves can melt the ice.
“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 explained. “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.”
Liquid water is the essential ingredient for life as we know it. If Mars once had water, it may once have sustained life. Understanding where this volcanic activity could have led to the existence of liquid water could also target the search for any possible fossilized remains of life.
“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,” he added. “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.”