Early Mars may have been more tectonically and volcanically active than previously thought. Evidence of tectonic activity around 4 billion years ago has been provided by 63 new examples of various volcanoes found in a strange region of Mars with strange properties that set it apart from the rest of the Martian highlands.
A team of planetary scientists has discovered that the landscape of the Eridania region of Mars, located in the planet’s southern hemisphere, appears to have been shaped in response to changes occurring in Mars’ crust, rather than from forces originating above or below it. The discovery could influence the search for signs of ancient life on the Red Planet, currently conducted by NASA’s Curiosity and Perseverance rovers.
“The large basins of this region were once home to a system of lakes known as paleolake Eridania, which was about a kilometer deep when the lake was at its greatest extent,” said team member Aster Cowart, a planetary geologist at the Institute for Planetary Science. , Aster Cowart. .with. “Long-lived volcanic vents near abundant water may have fueled hydrothermal systems that could have nurtured life.
“At the very least, these discoveries give us a greater number of places where we can look for evidence of life.”
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Unlike today’s Earth, modern Mars has little or no volcanic or tectonic activity. Furthermore, as about half of the Red Planet’s surface appears to be more than 3.5 billion years old, this suggests that crustal recycling has not happened extensively on Mars.
On Earth, the recycling of the Earth’s crust is driven by plate tectonics when one tectonic plate slides under another, causing surface material to be recycled into the mantle between the Earth’s crust and its molten core.
The team behind this new research studied the morphology and mineralogy of the Eridania region of Mars in the southern hemisphere using data from spacecraft around the Red Planet, including the Mars Global Surveyor, Mars Odyssey and the Mars Reconnaissance Orbiter.
“Several attributes of the Eridania region have attracted special attention for some time,” Cowart added. “Gamma-ray spectroscopy shows that this is a region of the crust with an especially distinct composition, gravitational data shows that it is generally less dense and thicker than the rest of the Martian crust, and magnetic data shows that it is an intensely magnetized. crust.”
They identified 63 examples of volcanism previously discovered in four different types of volcanoes: dome volcanics, stratovolcanoes, pyroclastic shields and caldera complexes.
The team suspects that the Eridania region alone contains hundreds of other examples of volcanic activity that are the remains of episodes of extreme geological activity on Mars about 3.5 billion years ago. They also think that the volcanic variety observed in this region could also be replicated in other regions of the Martian surface.
Tectonic activity gave impetus to early Mars
The type of geological activity observed on Mars through these observations is vertical tectonics, in which the land moves upward, causing uplift and subsidence. This was a precursor to the full plate tectonics we see on Earth today.
Cowart said the changes in the Earth’s crust behind these newly discovered volcanic features are analogous to a step Earth took on its own evolutionary path toward plate tectonics more than 2.5 billion years ago.
“Before the development of plate tectonics, it was difficult to recycle crust back into the mantle because the composition of the crust was more uniform, the crust was more rigid, and it was buoyant relative to the mantle,” Cowart continued. “However, the slow incorporation of water into the deeper levels of the crust began to cause mineral transformations that made the deep crust denser.”
Cowart explained that once enough of Earth’s lower crust underwent these mineral transformations, it began to sag into the mantle, a process known as “sagduction.” This pushed water-rich minerals that formed near Earth’s surface deeper into its crust, where they helped form floating magmas. The buoyancy of these magmas caused other regions of the crust to rise.
This resulted in a landscape dominated by large basins where the crust was sagging, mountain ranges where the crust rose, and volcanic rocks with a composition richer in silica than rocks from mantle sources.
“This is exactly what we see in the Eridania region,” Cowart said. “It’s really exciting to see a landscape so strongly shaped by pre-plate tectonic processes. Much of what we know about these processes on Earth is pieced together from heavily eroded ancient rocks that bear some degree of overprint from later plate tectonic activity. or where they occur in modern environments and are influenced by plate tectonic dynamics.”
This newly discovered geology of Mars could not only offer an opportunity to study a period of Earth’s past that is not accessible in our planet’s geological record, but it could also help determine how life arose on our planet.
This is because the processes behind these features may be analogous to origins of life scenarios that show living things emerging around porous hydrothermal vents, places where heated, mineral-laden seawater poured from cracks in the ocean crust. .
“It’s simply astonishing to think about the scale of activity in this region. Mars has a tendency to do everything on a grand scale, and to see a landscape almost the size of Europe or Arabia shaped by an interrelated set of tectonic processes in this amount of detail they are incredible”, concluded Cowart. “Seeing a Martian landscape
shaped by these processes and preserved in stasis offers us a great opportunity to investigate the evolution of the planetary landscape in a more detailed way.
The team’s research was published on Monday (12 February) in the journal Nature.