Tens of thousands of lava-like flows dot the surface of Mars, but a new study suggests not all of them are actually lava. Instead, some are mud volcanoes.
Mars has the tallest mountain in the Solar System, a volcano called Olympus Mons that's three times the size of Everest. This is just one of many examples of volcanism on the Red Planet. Yet despite thousands of lava-lilke flows, some don't display any other signs of volcanism. The team discovered they are likely sedimentary deposits, possibly formed after catastrophic floods. Water then seeped into the soil and eventually remerged as mud volcanoes.
Earth has mud volcanoes so their formation is certainly possible. However, Mars is colder and has a lower atmospheric pressure than Earth. To test their hypothesis, the team recreated the mud volcanoes in a lab. Using a vacuum chamber, they made mud flow at a fraction of Earth’s normal pressure and at a temperature well below zero. The results are published in Nature Geoscience.
"We suggest that mud volcanism can explain the formation of some lava-like flow morphologies on Mars and that similar processes may apply to eruptions of mud on icy bodies in the outer Solar System, like on Ceres," lead author Dr Petr Brož, from the Institute of Geophysics of the Czech Academy of Sciences, said in a statement.
Under Martian conditions, the water began to boil and evaporate due to the low pressure. The surface of the mud then froze due to the low temperature, which led to the formation of shapes similar to pahoehoe, the wavy structure formed by cooling lava seen typically in Hawaii.
The team believe the same process would be even more effective on dwarf planet Ceres due to the lack of atmosphere and colder temperature on the surface. It's also possible the process happens on other moons and dwarf planets in the solar system.
The authors conclude: "Our results show that it is vital to consider the effects of the differing environmental conditions on other planetary surfaces when comparing analogue landofrms observed on Earth with apparently similar effusive morphologies on other bodies."