The mysterious lava-like structures on the surface of Mars may have been caused by mud and not lava, according to a new study.
While these structures appear to look like pahoehoes – lava flows seen in Hawaii and Iceland – scientists believe they are actually a result of sedimentary volcanism, a geological phenomenon that causes mud to erupt from underground.
The findings, reported in the journal Nature Geoscience, have been described as “unexpected” and “very exciting” by lead author Dr Petr Broz, from the Institute of Geophysics of the Czech Academy of Sciences.
He said: “We have a tendency to expect that geological processes, like mud movement, would be operating elsewhere in the Solar System in a similar fashion as on Earth. This is based on our everyday experiences.
“However, our experiments clearly show that in reality, this simple process which we all know from our childhood would be very different on Mars.”
The Martian landscape is dotted with tens of thousands of these flow-like structures, some of which are hundreds of kilometres long and dozens of kilometres wide.
These channels were thought to have been a result of huge ancient floods but very little is known about these Martian landforms.
So the researchers performed a series of experiments in the Open University’s Mars Chamber, which simulates the surface conditions of the Red Planet.
The tests were carried out in low temperatures of around minus 20C, and low atmospheric pressure of around 7 millibars, to mimic the Martian environment.
They found that free-flowing mud under Martian conditions would behave differently from on Earth because of “rapid freezing and the formation of an icy crust”.
According to the researchers, this is because the atmosphere in Mars is very thin, about 150 times thinner than Earth’s, and its atmospheric pressure is less than 1% of the sea level pressure on Earth.
They said experiments under Martian conditions showed liquid mud “spilling from ruptures in the frozen crust, and then refreezing to form a new flow lobe”, resembling “mini versions” of pahoehoes.
Dr Manish Patel, senior lecturer in planetary sciences at The Open University, said the findings present a “potentially different geological history for Mars in terms of assumed volcanic activity”.
While Dr Susan Conway, a research scientist at CNRS in France, added: “Mars is always surprising us, I was amazed to see the experimental results with the mud forming lobes like mini-versions of the lava flows in Hawaii.
“These observations revolutionise the interpretation of many surface features mapped on the Martian surface.”