Mud on the Martian surface behaves very differently from Earth’s mud. In fact, the extremely low atmospheric pressure on the red planet makes liquid water unstable. Until now, it was unclear how the presence of various types of salts and their amounts would affect the properties of mud on the Martian surface.
An international team of scientists, led by Ondřej Krýza from the Geophysical Institute of the Czech Academy of Sciences, unraveled this dilemma investigating the mud behavior completing targeted experiments.
Their findings are now published in the journal Communications: Earth & Environment.
Cones and mudflows on the Martian northern lowlands
Because of Mars' extremely low atmospheric pressure (less than 1% of Earth's), liquid water cannot exist on the planet's surface. Consequently, it is challenging to predict how mud – a mixture of water and fine-grained rock fragments – would behave.
Nevertheless, in Mars' northern lowlands the presence of thousands of small cones and flows suggests that mud was extruded from the subsurface tens to hundreds of millions of years ago. These cones are Martian equivalents of Earth's mud volcanoes.
How did these mud flows form?
How could the mud flow in such low pressure conditions? And how mud flow for so long forming kilometer-sized structures? Could salt help in the propagation of mud over the Mars surface?
To understand how salts and their concentrations affect the mud behavior and the morphology of mud flows on the Martian surface, the team used a unique low-pressure chamber at the Open University in the UK.
While on Earth mixing salt into the mud may not significantly affect the mud behavior, the same principle may not be valid also for Mars. Ondřej Krýza, the leading author is the study, highlights this like this:
– We hypothesized that higher salt content would allow the mud mixtures to flow further by remaining in liquid state for longer periods of time. Surprisingly, the morphology of the mud flows is also significantly altered by varying salt concentrations.
– Higher salt content may even reduce the extension of the flows. Our experiments help to explain the paradox of mud volcanoes on Mars' surface, where conditions typically prevent mud from remaining in a liquid state.
Mudflows on Mars VS mudflows on Earth
The team’s new study and their results suggest that on Mars different salts and varying concentrations of salt will lead to the formation of distinctly different mud flows.
The shapes of the mud flows on March may resemble long strands of lava, wide pools, or short, fragmented lobes. Additionally, the surface color changes, which could aid in identifying mud structures through satellite observations.
Researcher Adriano Mazzini, Dept. of Geosciences, University of Oslo and IFE, part of the team, explains.
– On Earth, mud volcanoes and their mud flows feature a large variety of morphologies that are typically controlled by the type of erupted sediments, mud viscosity, pre-existing topography and, for large part, by the type of erosion.
– On Mars instead the salt type/concentration in the mud seems to be the primary factor in controlling the shape of the flows and their impressive extensions. A little bit of salt can make a big difference in Martian conditions. The vertical conduits of clastic eruption systems intersect different types of lithologies and distinct fluids-rock interactions can enrich the erupted mud with different types of salt. If we manage to decode the morphology of the mud flows and associate them with salt types and concentrations, we may ultimately also obtain information about the rock formations in the subsurface”, says Mazzini.
Salinity of the planets in the solar system
Salts are increasingly being detected by remote sensing not only on the surface of Mars but also on other bodies in the Solar System such as the dwarf planet, Ceres, where liquid water probably reached the surface in the past.
Here, as well as on the large icy moons of Jupiter and Saturn, it is assumed that a mixture of water, ammonia, hydrocarbons, and salts flowed to the surface in a process known as ‘cryo-volcanism’.
These could be an important host for potential microbial life forms. Hence, understanding the fundamentals of how salt-rich mixtures spread may play a crucial role in the search for life in the Solar System, concludes Adriano Mazzini.
Associated movie:
See this short movie on google drive about the trials on mud flow perfomed in this study: Are mud volcanos really on Mars?
Contact:
Researcher Adriano Mazzini, Department of Geosciences, University of Oslo, Norway.
Contact info | Phone: +47 22856108
The scientific article:
Krýza, O., Brož, P., Fox-Powell, M.G. et al. Small amounts of dissolved salts increase the mobility of mud flows on Mars and other extraterrestrial bodies. Commun Earth Environ 6, 116 (2025). https://doi.org/10.1038/s43247-025-02110-w