The relatively well-preserved ancient crust of Mars provides a natural window into early planetary evolution not available on Earth. Mars has generally been considered a one-plate basaltic planet, though recent evidence suggests magmatic evolution resulting in felsic crust might have occurred sporadically. New research shows multiple lines of evidence for diverse volcanism and complex volcanotectonics in the southern highlands of Mars within and around the 3.5 to 4-billion-year-old Eridania basin.
A topographic map of the Eridania region of Mars; volcanic structures described by Michalski et al. are classified by morphology and morphometrics. Image credit: Michalski et al., doi: 10.1038/s41550-023-02191-7.
Contrary to Earth, present-day Mars has little to no volcanic or tectonic activity.
Further, almost half of the planet’s surface is more than 3.5 billion years old, indicating that there has been no extensive crustal recycling — a phenomenon usually powered by tectonics such as those on Earth in which surface material is recycled into the mantle — since then.
Recent discoveries suggest that this was not always the case, but Mars’ geological activity in the first billion years after its formation is still unclear.
“Geological exploration of other rocky planets provides clues to early crustal evolution and volcanotectonic processes because other bodies exemplify comparable geosystems with variable mass, gravity and composition,” said Dr. Joseph Michalski from the University of Hong Kong and his colleagues.
“Observed through the lenses of different gravity fields, bulk planet compositions and heat flow, it is possible to test models for crustal resurfacing and so discover the steps that led to plate tectonics and other forms of crustal recycling.”
“The planet Mars represents a particularly valuable puzzle piece in this regard.”
The authors studied the morphology and mineralogy of the Eridania region in the southern hemisphere of Mars.
They analyzed remote sensing data from various orbiters, including NASA’s Mars Global Surveyor, Mars Odyssey, and Mars Reconnaissance Orbiter.
The Eridania region offers the strongest crustal remnants of Mars’ ancient magnetic field and various signatures of volcanism.
The researchers identified 63 instances of four different types of volcanoes (volcanic domes, stratovolcanoes, pyroclastic shields, and caldera complexes) with possibly hundreds more in the Eridania region alone, likely leftover from a vigorous period of geologic activity approximately 3.5 billion years ago.
This suite of observations is consistent with the presence of crustal recycling on early Mars driven by vertical tectonics, a kind of tectonic process precursor of full plate tectonics on Earth.
Such a variety of volcanic structures could be more widespread on ancient Mars than previously thought.
“The observed remnants of this activity may be the closest analogue on the planet to the hydrothermal origin of life scenarios proposed for Earth,” the scientists said.
Their paper was published today online in the journal Nature Astronomy.
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J.R. Michalski et al. Diverse volcanism and crustal recycling on early Mars. Nat Astron, published online February 12, 2024; doi: 10.1038/s41550-023-02191-7
